Federal highway numbers indicate the direction of the highway, the location and the significance of the highway.
Even numbers run east-west with the lowest numbers in the north, increasing as the highway numbers move south. Odd numbers run north-south with the lowest numbers in the east, increasing as they move west.
Highway numbers that end in zero travel the width of the continent. Highway numbers that end in one or five run from Canada to the Gulf of Mexico or to Mexico.
US 41 and US 45 are both significant highways that run virtually parallel in Michigan and Wisconsin (concurrently in some places) separating in Illinois and Indiana. US 41 terminates here, just outside Copper Harbor, Michigan and Miami, Florida. US 45 terminates in Ontonagon, Michigan (about 100 miles southwest of here) and in Mobile, Alabama.