Indiana State Route 3 is a north-south highway in Decatur County. It runs from the Rush/Decatur County Line, near Williamstown, to the Jennings/Decatur County Line, near Alert. IN St Rt 3 passes through the following towns in Decatur County. Sandusky Greensburg Westport Sardinia IN St Rt 3 is multi-plexed in Decatur County. Indiana State Route 46, from Greensburg to near Ewington. IN St Rt 3 intersects the following highways in Decatur County. Interstate 74, at Greensburg. U.S. Rt. 421, at Greensburg. Indiana State Route 46, at Greensburg. Indiana State Route 46, near Ewington.