Fredericksburg is a city in, and the seat of, Gillespie County, Texas, United States. As of the 2010 Census, this city had a population of 10,530.Fredericksburg was founded in 1846 and named after Prince Frederick of Prussia. Old-time German residents often referred to Fredericksburg as Fritztown, a nickname that is still used in some businesses. It is located 70 miles northwest of San Antonio, and approximately 80 miles west of Austin.