 US 41 was first designated as a US Highway in 1926 . A section of the highway originally served as part of Military Road , a connection between Fort Wilkins and Fort Howard during the Civil War . US 41 replaced the original M @-@ 15 designation of the highway which dated back to the formation of the Michigan state trunkline highway system . M @-@ 15 ran from Menominee through Marquette to Houghton and ended in Copper Harbor . Realignments and construction projects have expanded the highway to four lanes in Delta and Marquette counties and have created three business loops off the main highway . 
