| State: | IA |
| Type: | IA |
| Route: | 37 |
| Map Custom: | yes |
| Map Notes: | Iowa 37 highlighted in red |
| Length Mi: | 40.231 |
| Direction A: | West |
| Terminus A: | near Turin |
| Junction: | in Dunlap |
| Direction B: | East |
| Terminus B: | near Earling |
| Previous Type: | I |
| Previous Route: | 35 |
| Next Type: | IA |
| Next Route: | 38 |
Iowa Highway 37 (Iowa 37) is an east–west road in the west-central part of the state. Iowa 37 begins just east of Turin at Iowa Highway 175. It ends 4miles east of Earling at U.S. Highway 59. A small portion of the highway near Turin is designated as part of the Loess Hills Scenic Byway.
Iowa Highway 37 begins at an intersection with Iowa 175 east of Turin and adjacent to Iowa 175's crossing of the Maple River. The first NaNmiles of the route are part of the Loess Hills Scenic Byway.[1] The highway travels east and then southeast through the Loess Hills, a region of dunes east of the Missouri River created by wind-deposited silt from the Missouri River valley. At Soldier, Iowa 37 exits the Loess Hills and meets Iowa 183. From Soldier, the highway travels to the southeast to Dunlap. In Dunlap, Iowa 37 overlaps US 30 for NaNmiles. Eastbound Iowa 37 overlaps westbound US 30; this phenomenon is known as a wrong-way concurrency. Between Dunlap and Earling, Iowa 37 travels in a stairstep path to the south and east for . At Earling, the highway intersects the northern end of Iowa 191. Its last section is 4miles long, connecting Earling to US 59.
Originally, Iowa Highway 37 began at US 75 in Onawa to US 59 east of Earling. The westernmost 8miles of the route were overlapped by Iowa 175. In 1966, Iowa 37 was truncated to its current western end near the Maple River.[2] In 1971, a new section of US 59 was opened 1miles to the west of the former alignment. As a result, Iowa 37 was extended 1miles north and 6miles east to Irwin, absorbing Iowa 268[3] The section from US 59 to Irwin was short-lived. In 1980, the section east of US 59 was turned over to Shelby County.[4]