Interstate 15 in Utah

Interstate 15 Main route of the Interstate Highway System
Defined by Utah Code §72-4-107, maintained by UDOT
Length:	400.592 mi[1] (644.690 km)
South end:	I-15 towards Littlefield, AZ
Major junctions:	I-70 near Cove Fort I-80 in Salt Lake City I-84 in Riverdale
North end:	I-15 towards Malad, ID
State highways in Utah (lists: I • US • SR) < SR-14 SR-16 >

In the U.S. state of Utah, Interstate 15 runs north-south through the southwestern and central portions of the state, passing through many of the population centers of that state, including St. George, Provo, Salt Lake City, and Ogden, the latter three being part of the urban area known as the Wasatch Front. It is the primary north-south highway in Utah, as the majority of the state's population lives along its corridor. The only Metropolitan Statistical Area in Utah not connected via I-15 is the Logan Utah-Idaho Metropolitan Statistical Area.

Route description

The interstate passes through the fast-growing Dixie region, which includes St. George, Cedar City, and eventually most of the major cities and suburbs along the Wasatch Front, including Provo, Orem, Sandy, West Jordan, Salt Lake City, Layton, and Ogden. Around Cove Fort, Interstate 70 begins its journey eastward across the country. The interstate merges with I-80 for about 3 miles (5 km) from South Salt Lake to just west of Downtown Salt Lake City and also merges with Interstate 84 from Ogden to Tremonton. Along nearly its entire length through the state, I-15 winds its way along the western edge of a nearly continuous range of mountains (the Wasatch Range in the northern half of the state). The only exceptions are when it passes through the mountains south of Cedar City and again north of Cove Fort.

Extinct volcano cone near Fillmore, Utah off I-15.

I-15 begins at the Arizona/Utah border and heads northeast, continuing with two lanes in each direction. Right past the border, there is a port of entry on each side, making the first exit on the interstate in Utah going northbound. The route turns north past Bloomington before turning northeast again after the interchange with SR-18 to pass the eastern side of St. George. The highway continues northeast after exiting St. George and turns north-northeast north of Toquerville. South of Cedar City, the route turns east and north to pass through the west side of Cedar City and turns northeast again. Past a ranch exit (exit 100), the interstate turns northwest and then north to enter the western side of Beaver, with two interchanges serving that town. The road continues in a general north-northeast direction before intersecting with the western terminus of I-70. Past I-70, the route meanders to the north and northeast before straightening out to the northeast southwest of Kanosh. The highway passes the east side of both Meadow and Fillmore and the west side of Holden. The route turns north briefly after bypassing Scipio to the east before turning northeast. Past the interchange with SR-28 (which serves as a connector to I-70 for southbound I-15 motorists), the road passes the eastern side of Nephi. The interstate then turns northwest and north, bypassing Mona to the east.

Interstate 15 near New Harmony, south of Cedar City, looking north.

The highway enters the Wasatch Front and the Provo-Orem metropolitan area as it turns northeast and enters the town of Santaquin, where US-6 begins its overlap with I-15. Exiting Santaquin, the highway turns north and then northeast again to enter Payson. Continuing northeast, the route enters Spanish Fork and intersects with US-6 on the north side of town, where it turns north and gains one lane in each direction, the first time the interstate widens in the state. This interchange also marks the northern end end of the overlap with US-6. The route passes the west side of Springville and turns northwest south of Provo. The highway enters Provo and intersects with the southern terminus of US-189. Past this point, the interstate widens to four lanes in each direction. The route continues northwest, bisecting the west side of Provo. Past SR-114, the road loses one lane in each direction. Past SR-265, the highway once again widens to four lanes in each direction and gains an HOV lane begins. The lane gain is temporary and when the route turns north, the fourth lane is lost. At this point, the highway exits Provo and enters Orem. Right before the interchange at SR-241, the route turns northwest, entering Lindon. The route then exits Lindon and enters the south side American Fork, meandering between the west-northwest and northwest. The route straightens out the northwest and enters Lehi. In Lehi, US-89 begins an overlap with I-15. Past Lehi, the interstate exits the Provo metropolitan area and Utah County to enter the Salt Lake City metropolitan area.

I-15 in Salt Lake City

As the route enters the Salt Lake Valley from only one of three other points connecting Salt Lake County and Utah County (the others being SR-68 and Traverse Ridge Road), it turns northeast. Past SR-140, the highway widens to four lanes in each direction (not including the HOV lane) and turns north. The route enters Draper and turns north-northwest past SR-71, where US-89 ends its overlap with the interstate. As it enters Sandy, the interstate widens to five lanes past SR-151. The route straightens out to the north. The route turns north-northwest past SR-209 and soon after enters Midvale. The route intersects I-215, a beltway running through many of Salt Lake City's suburbs, in Midvale. Past this interchange, the route heads north and enters Murray. The route exits Murray and enters South Salt Lake, where an interchange with I-80 and SR-201 is located, colloquially known as the spaghetti bowl. The southern overlap of I-80 begins at this point. Also at this point, the highway enters Salt Lake City and a collector-distributor road begins at either side of the interstate, providing an exit to SR-201, 1300 South, and SR-270. After the collector-distributor ends, the route turns northwest to bypass downtown Salt Lake City. The route turns north after SR-269 and the northern end of the I-80 overlap. Past this point, the HOV lane ends and the highway loses one lane in each direction. Past the single-point urban interchange at SR-268, the interstate turns northwest and loses another lane. Before US-89, the road turns northeast briefly before turning north and entering Davis County.

The road enters North Salt Lake and I-215 defaults onto I-15 northbound. The route then gains two lanes in each direction and turns northeast. Past 2600 South, the highway turns north and enters Woods Cross to the west and Bountiful to the east. In West Bountiful, US-89 begins another overlap with I-15. The highway continues north and enters Centerville. The route exits Centerville and enters Farmington and turns northwest, US-89 exiting on its own separate freeway at an interchange (where the Legacy Parkway will terminate). The route passes through Kaysville, Layton, and Clearfield before turning north, passing the west side of Hill Air Force Base. The road continues north through Sunset before turning northeast through Roy. The interstate exits Davis County and enters Weber County. In Roy, I-84 defaults onto I-15 northbound and an overlap begins. The highway enters Ogden and the Ogden-Hinckley Airport is located on the west side of the highway. Past the airport, the route turns northwest before exiting Ogden and entering Marriott-Slaterville, where it straightens out to the north. Past Farr West, the highway turns northwest briefly before turning north and exiting Weber County, the Ogden-Clearfield metropolitan area, and the Wasatch Front.

I-15 warning sign for potentially drowsy drivers

The interstate continues north through Box Elder County. Brigham City, the county seat, is bypassed to the west by the freeway. Past US-91 (which continues to Logan and points northward), the route turns northwest to Tremonton, where I-84 separates, continuing northwest, and I-15 turns north. The freeway continues in this general direction until the Idaho border. The last exit northbound is located at exit 398, 25800 North, which provides a connection to the town of Portage.^[2]

History

This section requires expansion.

Legislative designation for I-15, until 1977

The southwest-north alignment followed by I-15 was a major transportation corridor in the early 20th century, followed by auto trails such as the Arrowhead Trail (south from Salt Lake City), Evergreen National Highway (entire length), and Banff-Grand Canyon Road (north from Nephi). In 1926, when the numbered system of U.S. highways was created, this route was signed U.S. Route 91^[3]

The route of I-15 from St. George to Brigham City was built along the corridor of what was U.S. Route 91 from 1926-1974.^[3] In 1974 I-15 was reasonably intact and US-91 was deleted, with the unfinished segments signed as Temporary I-15. The route north of Brigham City was built along the corridor of an old route of U.S. Route 191. This highway was also deleted once I-15 was reasonably intact. However, a different route in Utah was re-designated US-191 in 1982. ^[4]

Prior to 1977 the route of I-15 (and US-91 before) was also designated State Route 1 by the state of Utah, but no portion of the route was signed with this number.

In January 2009, the speed limit on two sections of I-15 together totaling 34 miles was raised to 80 mph as a "test," making Utah the second state to currently have speed limits greater than 75 mph.

Exit list

County	Location	Mile[1]	#		Destinations	Notes
			Old[5]
Washington	St. George	4.641		4	Brigham Road
		6.311		6	SR-18 / I-15 Bus. north (Bluff Street)
		8.662		8	I-15 Bus. south (St. George Boulevard, SR-34) to SR-18 – St. George, Santa Clara
	Washington	10.901		10	Washington City (SR-212)
		13.378		13	Washington Parkway
		15.908		16	SR-9 – Hurricane, Zion National Park
	Leeds	22.579		22	Leeds, Silver Reef (SR-228)	Northbound exit and southbound entrance
		23.703		23	Leeds, Silver Reef (SR-228)	Southbound exit and northbound entrance
	Toquerville	27.470		27	SR-17 – Toquerville, Hurricane
		30.682		30	Browse
		31.861		31	Pintura
		33.435		33	Ranch exit
		36.763		36	Ranch exit
		40.253		40	Kolob Canyons (Zion National Park)
		42.159		42	New Harmony, Kanarraville	Former SR-58
Iron		51.149		51	Hamilton Fort, Kanarraville	Former SR-58
	Cedar City	56.804		57	I-15 Bus. north (SR-130) to SR-14 – Cedar City
		58.837		59	SR-56 – Cedar City
		62.497		62	SR-130 (I-15 Bus. south) – Cedar City, Enoch, Minersville
		70.263		71	Summit, Enoch	Former SR-38
	Parowan	75.205		75	I-15 Bus. north / SR-143 – Parowan
		77.801		78	I-15 Bus. south (SR-274) to SR-143 – Parowan, Paragonah
		82.253		82	SR-271 – Paragonah
		94.453		95	SR-20 to US-89 – Panguitch, Kanab, Circleville
		99.690		100	Ranch exit
Beaver		108.745		109	I-15 Bus. north (SR-160) to SR-21 – Beaver, Milford
	Beaver	111.780		112	I-15 Bus. south (SR-160) to SR-21 – Beaver, Milford, Manderfield
		120.126		120	Manderfield
				125	Ranch exit	Closed
		129.443		129	Sulphurdale
Millard		132.183		132	I-70 east – Richfield, Denver
		134.875		135	Historic Cove Fort (SR-161)
		138.073		138	Ranch exit
		146.493		146	Kanosh	Former SR-133
	Meadow	158.265		158	SR-133 – Meadow, Kanosh
	Fillmore	163.370		163	I-15 Bus. north (SR-99) – Fillmore
		166.723		167	I-15 Bus. south (SR-99) – Fillmore
		173.507		174	To US-50 west (via SR-64) – Holden, Delta
		178.330		178	US-50 west – Holden, Delta	South end of US-50 overlap
		183.638		184	Ranch exit
		188.439		188	US-50 east – Scipio	North end of US-50 overlap
Juab		202.189		202	Yuba Lake
		206.553		207	Mills, Levan (SR-78)
	Nephi	222.812		222	I-15 Bus. north / SR-28 to I-70 – Nephi, Salina, Richfield
		225.266		225	SR-132 – Nephi, Manti
		228.091		228	I-15 Bus. south (SR-28) – Nephi, Delta
		233.161	236	233	SR-54 – Mona
Utah	Santaquin	242.447	245	242	South Santaquin
		244.809	248	244	US-6 west – Santaquin, Delta	South end of US-6 overlap
	Payson	248.845	252	248	Payson, Salem (SR-178)
		250.923	254	250	SR-115 – Payson, Benjamin
		253.557	256	253	SR-164 – Spanish Fork, Benjamin
	Spanish Fork	257.264	260	257	SR-156 – Spanish Fork
		257.636	261	258	US-6 east to US-89 – Price, Manti	North end of US-6 overlap; northbound exit is via exit 257
	Springville	259.976	263	260	SR-77 – Springville
		261.821	265	261	SR-75 – Springville, Provo
	Provo	263.373	266	263	US-189 north (University Avenue) / 1860 South
		265.589	268	265	SR-114 (Center Street) – Provo, Provo Municipal Airport	Signed as exits 265A (east) and 265B (west) northbound
	Orem	269.072	272	269	SR-265 (University Parkway)
		270.660	274	271	Center Street – Orem
		271.670	275	272	SR-52 (800 North) to US-189
	Lindon	272.767	276	273	1600 North (SR-241) – Lindon
	Pleasant Grove	275.328	278	275	Pleasant Grove, Lindon
	American Fork	276.501	279	276	500 East (SR-180) – American Fork, Pleasant Grove
		278.586	281	278	Main Street (SR-145) – American Fork
	Lehi	279.701	282	279	SR-73 west (Main Street) – Lehi
		282.311	285	282	US-89 south / 1200 West – Lehi	South end of US-89 overlap
		283.985	287	284	SR-92 – Highland, Alpine
Salt Lake	Draper	288.272	291	288	SR-140 (14600 South)
		289.832	293	289	SR-154 (Bangerter Highway)
		291.358	294	291	SR-71 (12300 South, US-89 north)	North end of US-89 overlap
	Sandy	293.634	297	293	SR-151 (10600 South)
		295.616	298	295	SR-209 (9000 South)
	Midvale	297.920	301	297	SR-48 (7200 South)
	Murray	299.005	302	298	I-215 (Belt Route)
		300.300	303	300	SR-173 (5300 South)
		301.653	304	301	SR-266 (4500 South)
	South Salt Lake	303.414	306	303	SR-171 (3300 South)
		304.691	307	304	I-80 east  – Cheyenne	South end of I-80 overlap
		305.231	308A	305A	SR-201 west – West Valley
		305.198	308B	305B	2100 South (SR-201)
	Salt Lake City	306.315	309A	305C	1300 South
		306.607	309B	305D	900 South (SR-270)	Northbound exit and southbound entrance
		307.500	310	306	600 South (SR-269)	Northbound exit and southbound entrance
		307.740	310	307	400 South	Northbound exit and southbound entrance are HOV-only
		308.079	311	308	I-80 west – Salt Lake International Airport, Reno	North end of I-80 overlap
		309.333	312	309	600 North (SR-268)
		310.239	313	310	900 West	No northbound exit
		311.792	314	311	2300 North
		311.947	315	312	US-89 south (Beck Street)	Southbound exit and northbound entrance
Davis	North Salt Lake	313.128	315	312	US-89 north	Northbound exit and southbound entrance
		313.275	316	313	I-215 south (Belt Route) – Salt Lake Airport	Southbound exit and northbound entrance
		314.301	317	314	Center Street	Southbound exit only
		315.243	318	315	2600 South (SR-93)
	Woods Cross
		316.870	320	316	SR-68 (500 South)
	Bountiful
	West Bountiful
		317.557	321	317	400 North (SR-106)	Northbound exit and southbound entrance
		318.024	321	317	US-89 south	South end of US-89 overlap; southbound exit and northbound entrance
	Bountiful
	Centerville	319.512	322	319	Centerville (SR-105)
	Farmington	322.916	325	322	SR-227 / Lagoon Drive – Farmington	Northbound exit and southbound entrance
		324.026	326	324	US-89 north to I-84 east – South Ogden	North end of US-89 overlap; northbound exit and southbound entrance
		324.243			Legacy Parkway	Southbound exit and northbound entrance
		324.741	327	325	SR-225 / Lagoon Drive – Farmington	Northbound exit is via exit 324
	Kaysville	328.640	331	328	SR-273 – Kaysville
	Layton	330.019	332	330	I-15 Bus. north / SR-126 – Layton	Northbound exit and southbound entrance
		331.589	334	331	SR-232 (Hill Field Road) – Layton
		332.883	335	332	SR-108 (Antelope Drive) – Antelope Island
	Clearfield	334.066	336	334	SR-193 (700 South)
		335.800	338	335	SR-103 (650 North)
Weber	Roy	338.447	341	338	SR-97 (5600 South)
	Riverdale	339.133	342	339	SR-26 (Riverdale Road) to I-84 east	Northbound exit and southbound entrance
		340.227	343	340	I-84 east – Riverdale, Cheyenne	South end of I-84 overlap; northbound exit is via exit 339
	Ogden	341.948	344	341	SR-79 (31st Street)
		343.067	345	342	SR-53 (24th Street)	Northbound exit and southbound entrance
	West Haven	343.852	346	343	SR-104 (21st Street, Wilson Lane) – Ogden City Center
	Marriott-Slaterville	344.968	347	344	SR-39
		346.726	349	346	Harrisville
	Farr West	349.361	352	349	SR-134 – Farr West, Pleasant View, North Ogden
Box Elder		351.853	354	351	SR-126 to US-89 – Willard, Pleasant View
	Willard	357.554	360	357	SR-315 – Willard, Perry
		358.566	361		Port of Entry
		360.542	363		Rest Area	Northbound exit and entrance
		362.020	364	362	US-91 (1100 South Street, I-15 Bus. north, I-84 Bus. west) to US-89
	Brigham City	363.738	366	363	Forest Street
		365.508	368	365	SR-13 (900 North Street, I-15 Bus. south, I-84 Bus. east)
	Honeyville	372.734	375	372	SR-240 to SR-13 – Honeyville, Bear River
	Tremonton	376.532	379	376	SR-13 (I-15 Bus. north, I-84 Bus. west) – Tremonton, Garland, Bear River
		379.334	382	379	I-84 west (SR-30 west) – Tremonton, Boise	North end of I-84 overlap; south end of SR-30 overlap
	Tremonton	381.037	383	381	I-15 Bus. south – Tremonton, Garland
		385.266	387	385	SR-30 east – Riverside, Logan	North end of SR-30 overlap
		392.387	394	392	SR-13 south – Plymouth
		398.817	402	398	Portage	Former SR-90

References

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