Chicago and San Jose are about 1,838 miles apart by road. Split the difference and you arrive near Denver, the city closest to the halfway point between them. That splits the trip almost evenly — about 19 hr 15 min from Chicago and 19 hr 26 min from San Jose.
Over this distance most people will fly rather than drive the whole way. Denver still makes a fair, central place for Chicago and San Jose to converge, splitting the travel instead of asking one side to cross the country.
If Denver doesn't have what you're after, Albuquerque and Salt Lake City are also close to the midpoint and worth a look — each keeps the drive reasonably balanced between Chicago and San Jose.
City descriptions adapted from Wikipedia (CC BY-SA); photos via Wikimedia Commons, credited above.