Its eastern terminus at Illinois Route 127 at a rural intersection west of with Illinois Route 157 and Illinois Route 159 in Edwardsville, and Illinois Route 160 and U.S. Route 40 in Highland.
Its eastern terminus at Illinois Route 127 at a rural intersection west of Tamalco. Illinois 143 is multiplexed with Illinois Route 157 and Illinois Route 159 in Edwardsville, and Illinois Route 160 and U.S. Route 40 in Highland.