The fair place to meet is Denver, CO — the city closest to the midpoint of Indianapolis and Seattle. From the farther side that’s about 21 hr 23 min of driving.
Recommended midpoint
Denver, CO
From Indianapolis
20 hr 56 min
999 mi to Denver
From Seattle
21 hr 23 min
1,020 mi to Denver
Indianapolis has the shorter trip; the split is off by about 27 min. The alternatives below can even it out. Indianapolis and Seattle are about 1,868 miles apart.
Indianapolis and Seattle are about 1,868 miles apart by road. Split the difference and you arrive near Denver, the city closest to the halfway point between them. That puts roughly 20 hr 56 min of driving on the Indianapolis side and 21 hr 23 min on the Seattle 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 Indianapolis and Seattle to converge, splitting the travel instead of asking one side to cross the country.
If Denver doesn't have what you're after, Salt Lake City and Omaha are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Indianapolis and Seattle.
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 →
Indianapolis, colloquially known as Indy, is the capital and most populous city of the U.S. state of Indiana and the county seat of Marion County. Indianapolis is situated in the state's central till plain region along the west fork of the White River. Read more →
Seattle is the most populous city in the U.S. state of Washington and the Pacific Northwest region of North America. 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.