The Shore to Shore trail... well, there are two of them, Michigan and Florida, but MI is horse and hikers only. FLA isn't so stupid. Both trails are roughly 240 miles long

It is through a national wildlife refuge, Canaveral National Seashore and Kennedy Space Center, and connects with the East Coast Greenway, a 2900-mile stretch of trails connecting Maine to Key West

250 miles long and currently more than 80 percent complete. The trail will link communities between St. Petersburg and the Canaveral National Seashore.

Florida has 54 rails to trails, and 780 miles total

there are still some areas to be finished... there were 4 gaps between existing trails.

On the flip side:

Michigan, long known for doing stupid things (ask anyone about the Michigan DNR for example, or having a time zone line one county away from the damn border with Wisconsin)

the Michigan Shore-to-Shore Trail 230 miles across the northern Lower Peninsula of Michigan, that runs between Sleeping Bear Dunes on Lake Michigan to Oscoda on Lake Huron roughly adjacent to hwy 72 It is open to horseback riders and hikers but not bicycles. Seems like they could give bikers a week in spring, and one in the fall, and not allow horses.... just how damn many people are riding horses across states anyway?

The trail, going from west to east, travels through the Boardman River valley and follows the Au Sable River for about 50 miles. The trail was developed by trail riders in 1962 and travels through mixed hardwood and conifer forests. Public campgrounds are located throughout the route.

https://www.railstotrails.org/our-work/united-states/florida/#state
http://fgtf.org/projects/coast-to-coast-connector/
https://www.bikeflorida.net/coast-to-coast.htm
https://floridadep.gov/parks/ogt/content/florida-coast-coast-trail
https://floridahikes.com/coast-to-coast-trail