Westchester is a census-designated place and neighborhood in Miami-Dade County, Florida. It is part of the Miami metropolitan area of South Florida. Prior to the 2020 U.S. Census, the neighboring University Park CDP was merged into Westchester CDP, effectively doubling its geography and population. Per the 2020 census, the population was …Westchester is a census-designated place and neighborhood in Miami-Dade County, Florida. It is part of the Miami metropolitan area of South Florida. Prior to the 2020 U.S. Census, the neighboring University Park CDP was merged into Westchester CDP, effectively doubling its geography and population. Per the 2020 census, the population was 56,384.