40 U.S.C. § 902

(A)

a geographical area within the jurisdiction of an incorporated city, town, borough, village, or other unit of general local government, except a county or parish, having a population of at least 10,000 inhabitants;

(B)

that portion of the geographical area within the jurisdiction of a county, town, township, or similar governmental entity which contains no incorporated unit of general local government but has a population density of at least 1,500 inhabitants per square mile; and

(C)

that portion of a geographical area having a population density of at least 1,500 inhabitants per square mile and situated adjacent to the boundary of an incorporated unit of general local government which has a population of at least 10,000.