Alexander City, known to locals as "Alex City", is the largest city in Tallapoosa County, Alabama, United States, with a population of 14,…Alexander City, known to locals as "Alex City", is the largest city in Tallapoosa County, Alabama, United States, with a population of 14,843 as of the 2020 census. It has been the largest community in Tallapoosa County since 1910. It is known for Lake Martin with its 750 miles of wooded shoreline and 44,000 acres of water. Lake Martin stands on the Tallapoosa River and offers boating, swimming, fishing, golfing, and camping. Many neighborhoods and luxury homes are located on the lake.