sentences:  The remaining three islands in the U.S. Minor Outlying Islands (Midway Atoll, Palmyra Atoll and Wake Island) have small non-permanent human populations.The county-equivalent with the smallest non-zero population counted in the census is Swains Island, American Samoa (17 people), although since 2008 this population has not been permanent either.The most densely populated county or county-equivalent is New York County, New York (coextensive with the New York City Borough of Manhattan), with 72,033 persons per square mile (27,812/km2) in 2015.