New York's most populous county in 2019 is Kings County, or the Brooklyn borough, with a population of 2,648,771. This represents growth of 5.49% since the 2010 census. New York is home to many counties and/or boroughs with more than 1 million people including Queens County (2,358,582), New York County (1,664,727), Suffolk County (1,492,953), Bronx County (1,471,160), and Nassau County (1,369,514). With the exception of Suffolk County (-0.12%), all of these counties have reported population growth of at least 2%.
Hamilton County is the least populated county in New York with 4,485 residents, a decline of 7.58% since the census. This is the only New York county under 15,000 people. There are a few other counties under 30,000 people in New York including Schuyler County (18,000), Yates County (24,955), and Lewis County (24,955). All of these counties -- in fact, all New York counties with fewer than 100,000 people -- have experienced a population decline.
Bronx County, which has the same boundaries as the Bronx borough, has experienced the most population growth since the census, increasing by 5.98% to 1,471,160. The only other counties with growth above 5% are Kings County and Queens County (5.49% each) and Rockland County (5.22%). Most counties in New York have lost residents since the 2010 census. The county that has experienced the greatest decline since 2010 is Hamilton County at -7.58% growth to 4,485. Other major declines occurred in Delaware County (-6.03%) and Chenango County (-5.03%).