Wayne County is the most populous county in the U.S. state of Michigan. As of 2020, the United States census placed its population at 1,793,561, making it the 19th-most populous county in the United States. The county seat is Detroit. The county was founded in 1796 and organized in 1815. Wayne County is included in the Detroit-Warren-Dearborn, MI Metrop…Wayne County is the most populous county in the U.S. state of Michigan. As of 2020, the United States census placed its population at 1,793,561, making it the 19th-most populous county in the United States. The county seat is Detroit. The county was founded in 1796 and organized in 1815. Wayne County is included in the Detroit-Warren-Dearborn, MI Metropolitan Statistical Area. It is one of several U.S. counties named after Revolutionary War-era general Anthony Wayne.