The route begins at New Sharon's western city limit where it continues as Mahaska County Road G5T and ends at the corner of Market and Main Streets in New Sharon, where U.S. Route 63 and Iowa Highway 146 intersect.

It turned to the east and headed to the northeast in a stairstep path for 3+3⁄4 miles (6.0 km).

Now at the western city limits of New Sharon, the current extent of Iowa 102 begins.

In the mid-1980s, the western end moved to what is now 240th Place in Mahaska County, just east of Pella.

On December 23, 2002, the Mahaska County Board of Supervisors voted unanimously to accept 15.4 miles (24.8 km) of the 15.9-mile-long (25.6 km) route, extending from the Iowa Highway 163 bypass to the western city limits of New Sharon[5] leaving only the half-mile segment in New Sharon on the state rolls.