The fair place to meet is Denver, CO — the city closest to the midpoint of Boise and Nashville. From the farther side that’s about 21 hr 24 min of driving.
Recommended midpoint
Denver, CO
From Boise
13 hr 21 min
637 mi to Denver
From Nashville
21 hr 24 min
1,020 mi to Denver
Boise has the shorter trip; the split is off by about 8 hr 3 min. The alternatives below can even it out. Boise and Nashville are about 1,632 miles apart.
Boise and Nashville are about 1,632 miles apart by road. Split the difference and you arrive near Denver, the city closest to the halfway point between them. That puts roughly 13 hr 21 min of driving on the Boise side and 21 hr 24 min on the Nashville side — the fairest single meeting point among the cities near the middle.
Over this distance most people will fly rather than drive the whole way. Denver still makes a fair, central place for Boise and Nashville to converge, splitting the travel instead of asking one side to cross the country.
If Denver doesn't have what you're after, Omaha and Kansas City are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Boise and Nashville.
Denver is the capital and most populous city of the U.S. state of Colorado. Officially a consolidated city and county, it is located in the South Platte River valley on the western edge of the High Plains, and is just east of the Front Range of the Rocky… Read more →
Boise is the capital and most populous city in the U.S. state of Idaho. It is the county seat of Ada County. The population of the city was 235,685 at the 2020 census. Read more →
Nashville is the capital and most populous city in the U.S. state of Tennessee. It is the seat of Davidson County in Middle Tennessee, located on the Cumberland River. Read more →
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.
Estimates use straight-line distance and typical road speeds; real drive times vary with route and traffic.