British Columbia.
Obviously Alaska is north of Idaho. States in the "Lower 48" that have significant amounts of terrain farther north than the northern border of Idaho include Washington and Maine. Minnesota has a little tip that seems to be slightly farther north than Idaho, but if it is, it's not by much. The Canadian province of British Columbia abuts Idaho's northern border.
If you traveled north from the Great Salt Lake to the Canadian border, you would primarily pass through Utah and then into Idaho. Depending on your exact route, you may also briefly enter Wyoming. Finally, you would reach the Canadian border in northern Idaho.
Montana if you are in Wyoming or southern or central Idaho Canada if you are in Canada or the dakotas or northern Idaho
Idaho is the state on the Canadian border that is home to Coeur d'Alene, Downey, Idaho Falls, and Pocatello.
Idaho does
The State of Montana is bordered on the East by North Dakota and South Dakota, to the South by Wyoming, and to the West and South by Idaho. The Northern border of Montana is also the U.S./Canadian border (Canadian Provinces of Alberta and Saskatchewan).
Washington State's northern border with Canada is a straight line from Blaine WA to its eastern border with Idaho. That northern border line is the most northern point.
The 42nd parallel forms the southern boundary of Idaho. It marks the border between Idaho and Nevada as well as a portion of the border between Idaho and Oregon.
It is a Western state between Idaho and North Dakota on the Canadian border.
Washington and Idaho
Idaho is closer to Canada than South Dakota. The northern border of Idaho shares a boundary with Canada, while South Dakota's northern border is further south and does not directly connect to Canada. The distance from Idaho to Canada is significantly shorter compared to that from South Dakota.