High Quality Content by WIKIPEDIA articles! M-331 is an unsigned state trunkline highway in the U.S. state of Michigan located within the city of Kalamazoo. It runs from the southern city limits north into downtown Kalamazoo. This was one of many highways to be established or realigned as a result of a rationalization process initiated in 1998 during the tenure of Governor John Engler. M-331 uses streets in Kalamazoo that were once part of US Highway 131 (US 131) before a freeway was built that bypassed the downtown area.