Of the 2,442 or so current NHLs, 3 states, Pennsylvania, Massachusetts, and New York account for nearly 25 percent of the nation's NHLs. In addition to these states, cities within these states, Boston, Philadelphia, and New York City (each separately) alone have more NHLs than 40 out of the 50 states. There are NHLs in all 50 states. There are 74 in the District of Columbia, 15 in Puerto Rico and other U.S. commonwealths and territories, five in U.S.-associated states such as Micronesia, and one in Morocco.