U.S. Route 45 is a major north-south United States highway and a border-to-border route, from Lake Superior to the Gulf of Mexico. A sign at the highway's northern terminus notes the total distance as. US 45 is notable for incorporating, in its maiden alignment, the first paved road in the South, a 49-mile segment in Lee County, Mississippi. Let to contract in July 1914, the concrete highway opened on November 15, 1915. As of 2006, the highway's northern terminus is in Ontonagon, Michigan, at the corner of Ontonagon and River Streets, a few blocks from Lake Superior. US 45's southern terminus is in Mobile, Alabama, at an intersection with U.S. Route 98.
U.S. Highway 45 is part of a designated hurricane evacuation route in Mississippi. It is entirely four-laned from its point of entry from Alabama, at the town of State Line, to the Tennessee line just north of Corinth, along the way serving the towns of Waynesboro, Meridian, Columbus and Tupelo. At Brooksville, U.S. 45 splits away from U.S. 45 Alternate and serves the towns of Columbus and Aberdeen before rejoining U.S. 45 Alternate south of Tupelo. The alternate roadway provides a more direct and entirely four-laned route between Meridian and Tupelo, bypassing Columbus to the west and, more closely, Starkville to the east. Major junctions of U.S. 45 in Mississippi include U.S. Route 84 at Waynesboro, Interstate 20/59 at Meridian, U.S. Route 82 at Columbus, Interstate 22/U.S. Route 78 at Tupelo and U.S. Route 72 at Corinth. Each of these junctions is an interchange and, with the exception of Waynesboro, each is part of a freeway segment. The Mississippi section of U.S. 45 is defined at Mississippi Code Annotated § 65-3-3.
Tennessee
Southern section From the Mississippi state line, US 45 extends north past the cities of Guys, Eastview, Selmer, Bethel Springs, Finger, Henderson, Pinson, and Jackson to Three Way, where the highway splits into US 45W and US 45E. U.S. Route 45W U.S. Route 45W is a state highway in West Tennessee, connecting Jackson with South Fulton via Humboldt, Trenton, Rutherford, and Union City. For the majority of its length, it is concurrent with unsigned State Route 5. U.S. Route 45E U.S. Route 45E is a state highway in West Tennessee, connecting Jackson with South Fulton via Milan and Martin. For the majority of its length, it is concurrent with unsigned State Route 43 for most of the route's length except for short segments at Martin and South Fulton, where it is cosigned with SR 216 and SR 215 respectively. Northern section Mainline US 45, concurrent with unsigned SR 3, goes northeast and passes through neighborhoods in South Fulton along Chickasaw Drive before turning north onto Highland Drive at an intersection with Kentucky Route 116 at the western edge of downtown. US 45 then crosses into Kentucky and the city of Fulton.
Kentucky
U.S. 45 enters Kentucky at Fulton then northeast past Mayfield then heads directly north into Paducah as a four-lane highway. In Paducah, U.S. 45 serves as a major artery, intersecting with Interstate 24 at exit 7, and intersecting US 60 and 62. U.S. 45 leaves Kentucky from Paducah's northern border across the two-lane, metal-grate Brookport Bridge to Brookport, Illinois across the Ohio River.
US 45 enters Michigan south of Watersmeet. From there, the highway crosses the Western Upper Peninsula through the Ottawa National Forest running north to Ontonagon. US 45 ends just south of Lake Superior in downtown Ontonagon. The terminus was not changed in 2006 despite realignment then of M-38 and M-64 from the terminus to a crossing south.
