Interstate 43 is an Interstate Highway in the state of Wisconsin in the United States . Interstate 43 ( I-43 ) is a 191.55 m intrastate Interstate Highway located entirely within the U.S. state of Wisconsin , connecting Interstate 39 and Interstate 90 in Beloit with Milwaukee and U.S. Route 41 and U.S. Route 141 in Green Bay . I-43 is the 5th longest intrastate Interstate Highway of the Interstate Highway system .