From its southern terminus, SH-37 heads northwest briefly before turning north to pass through Roy.

It then continues north through farmland and passes through the town of Rockland before ending at a diamond interchange with I-86/US 30 southwest of American Falls.

Interstate 86 Business continues from the interchange on Frontage Road and heads east toward American Falls.

[1][2] By 1927 the SH-37 designation had been assigned to a route south-east of Coeur d'Alene in the northern part of the state.

[5] Eventually, the routing of SH-38 was changed to its current route, with the roads through Buist, Arbon, and Crystal to Portneuf being entirely removed from the state highway system; as well as the section that was previously part of SH-37 between Holbrook and the Power County-Oneida County line.