New Rochelle is a city in Westchester County, New York, United States, in the southeastern portion of the state. In 2020, the city had a population of 79,726, making it the seventh-largest in the state of …New Rochelle is a city in Westchester County, New York, United States, in the southeastern portion of the state. In 2020, the city had a population of 79,726, making it the seventh-largest in the state of New York. Some residents refer to the city as New Ro or New Roc City.