RCW 35.13.190: Annexation of federal areas by second-class cities and towns.

Any unincorporated area contiguous to a second-class city or town may be annexed thereto by an ordinance accepting a gift, grant, or lease from the government of the United States of the right to occupy, control, improve it or sublet it for commercial, manufacturing, or industrial purposes: PROVIDED, That this shall not apply to any territory more than four miles from the corporate limits existing before such annexation.