City of McKinney From its historic downtown square to its state-of-the-art planned communities, McKinney’s mix of traditional values and contemporary vision makes it a unique and desirable place to visit, conduct business, explore and live. Collin County Welcome to the official website of Collin County, Texas! We are the home to more than 660,000 citizens, spreading out over 885 square miles of Texas. Come to our site to find out how you can work, play, and live in Collin County.