SR 3 begins just south of Charlestown at SR 62 and heads north toward downtown Charlestown. When in downtown Charlestown SR 3 intersects SR 403. SR 3 heads north out of Charlestown. Then just over north of SR 403, there is a wrong-way concurrency with SR 203 for , meaning southbound SR 203 and northbound SR 3 are going the same direction. After SR 203, SR 3 heads north toward Vernon and then North Vernon. In North Vernon SR 3 has an intersection with U.S. Route 50 (US 50). After North Vernon SR 3 heads mainly due north for until SR 46 just west of Greensburg. SR 3 joins SR 46 on a four-lane divided highway and then enters Greensburg from the southwest. After entering Greensburg SR 46 leaves SR 3 at Main Street. In downtown Greensburg SR 3 has an intersection with US 421.