How Many U.S. Troops Are On Okinawa?

Okinawa measures 454 square miles, almost exactly the size of Los Angeles. Although World War II ended with the Japanese surrender in 1945, the island still contains 39 U.S. bases.
42,962 Americans troops inhabit the island (Source: Okinawa: Asia's Last Colony, pp. 34-64.
Chalmers Johnson, Blowback: The Costs and Consequences of American Empire).

For comparison's sake, the U.S. Troop level in Iraq during December 2007 was 160,000.

The United States maintains 3,731 military installations worldwide.
Source:
DEPARTMENT OF DEFENSE
BASE STRUCTURE REPORT, 2006.