Onondaga County Located in the center of New York State, Onondaga County is home to the city of Syracuse. We are within 350 miles of all major cities in the Northeast, conveniently situated at the intersection of Interstate Highways 81 and 90 (NYS Thruway). The County of Onondaga is located in the central New York region, has a land area of 793.5 square miles and is approximately 35 miles in length and 30 miles in width. TThe 2000 U.S. Census showed a population of 458,336 for Onondaga County, which included a population of 147,306 for the City of Syracuse. The City of (2 comments)