Latitudes and longitudes require a direction as well as a measurement; latitudes are north or south of the equator, while longitudes are east and west of the Prime Meridian. So your question has four possible answers.
42N 123W: On the California/Oregon border.
42N 123E: Near Ban Jiatuncun, China
42S 123E: In the Indian ocean, 500 miles south of Australia
42S 123W: In the South Pacific Ocean, a VERY long way from any land at all. About halfway between New Zealand and South America.
A city at 42 degrees north latitude and 73 degrees west longitude could be Syracuse, New York, in the United States.
42 degrees North, 82 degrees West
41 degrees latitude and 83 degrees longitude
Elmhurst is located in the state of New York. The latitude and longitude of Elmhurst is 42 degrees north and 79 degrees west.
Latitude: 51°02′42″N Longitude: 114°03′26″W
The longitude of the State of Missouri is 89 degrees 6'W to 95 degrees 42'W. The Latitude is 36 degrees N to 40 degrees 42'W. The longitude and Latitude of the Missouri River would depend on what location you are researching.
Greenland.
Rome, Italy is located at 42 degrees North Latitude and 13 degrees East Longitude.
A city at 42 degrees north latitude and 73 degrees west longitude could be Syracuse, New York, in the United States.
Latitude :N 42° 32' 46.482", Longitude: E 1° 36' 5.5944"
40° 6′ 1″ N, 123° 47′ 42″ W
Italy.
42 degrees North, 82 degrees West
41 degrees latitude and 83 degrees longitude
Latitude: N 42° 53' 11.2092" / Longitude: W 78° 52' 42.1284"
Elmhurst is located in the state of New York. The latitude and longitude of Elmhurst is 42 degrees north and 79 degrees west.
Ithica, New York is located in south central New York. Its exact coordinates are 42 degrees, 26 minutes North, 76 degrees, 30 minutes West.