The fair place to meet is Denver, CO — the city closest to the midpoint of Boise and Milwaukee. From the farther side that’s about 19 hr 8 min of driving.
Recommended midpoint
Denver, CO
From Boise
13 hr 21 min
637 mi to Denver
From Milwaukee
19 hr 8 min
913 mi to Denver
Boise has the shorter trip; the split is off by about 5 hr 47 min. The alternatives below can even it out. Boise and Milwaukee are about 1,416 miles apart.
Boise and Milwaukee are about 1,416 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 19 hr 8 min on the Milwaukee 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 Milwaukee 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 Minneapolis are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Boise and Milwaukee.
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 →
Milwaukee is the most populous city in the U.S. state of Wisconsin. It is located on the western shore of Lake Michigan at the confluence of the Milwaukee, Menomonee, and Kinnickinnic Rivers. 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.