Lavon is a city in Collin County and has been one of the U.S. state of Texas's fastest-growing communities, with a 2000 census-tabulated …Lavon is a city in Collin County and has been one of the U.S. state of Texas's fastest-growing communities, with a 2000 census-tabulated population of 387 and 2020 tabulated population of 4,469. Lavon, Texas, is a city located in southeastern Collin County. The city is situated approximately 1 mile southeast of Lavon Dam on the East Fork of the Trinity River, which forms Lavon Lake, a key recreational and water supply resource for the region. According to the United States Census Bureau, Lavon encompasses a total area of 2.4 square miles, with 0.01 square miles, or 0.39%, accounted for by water.