I-75 is one of the most heavily traveled interstates, second in cars per mile to I-95.
The northern terminus is Sault Ste. Marie on the north shore of Michigan's Upper Peninsula. South from there, I-75 traverses a bit of the U.P., and crosses the Mackinac Bridge, one of the longest suspension bridges in the world. It bisects the Lower Peninsula of Michigan, sweeping to the east to pass through Detroit, then directly southward for Toledo, Dayton, and Cincinnati in Ohio, and Lexington in Kentucky. It then tacks to the east to hit Knoxville and Chattanooga, Tennessee, then west to Macon and Atlanta, Georgia. From there it is south to the Tampa area and south along Florida's gulf coast until it heads due east for Miami.
Interesting facts:
I-75 crosses the Great Miami River near Dayton five times. 2000 miles away it hits the city of Miami.
There are no exits to residential streets anywhere along I-75.