Omaha and Philadelphia are about 1,091 miles apart by road. Split the difference and you arrive near Indianapolis, the city closest to the halfway point between them. That puts roughly 10 hr 59 min of driving on the Omaha side and 12 hr 13 min on the Philadelphia 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. Indianapolis still makes a fair, central place for Omaha and Philadelphia to converge, splitting the travel instead of asking one side to cross the country.
If Indianapolis doesn't have what you're after, Cincinnati and Chicago are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Omaha and Philadelphia.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.