The most extensive county or county-equivalent is the Yukon-Koyukuk Census Area, Alaska, with a land area of 145,505 square miles (376,856 km2). All nine of the most extensive county-equivalents are in Alaska. The most extensive county is San Bernardino County, California, with a land area of 20,057 square miles (51,947 km2). The least extensive county is Kalawao County, Hawaii, with a land area of 11.991 square miles (31.058 km2). The least extensive county-equivalent in the 50 states is the independent city (United States) Falls Church, Virginia, with a land area of 1.999 square miles (5.177 km2). If U.S. territories are included, the least extensive county-equivalent is Kingman Reef, with a land area of 0.01 square miles (0.03 km2).. How many more square miles is San Bernardino County than Kalawao County?