Mason County Courthouse, Mason, Texas. Recorded Texas Historic Landmark - 1988 – GeoffreyLong, CC BY-SA 3.0 – Wikimedia Commons Mason is located in Mason County. About 2,121 people live here (as of 2020). Between 2010 and 2020, the population grew from 2,114 to 2,121. The region is at 469 meters above sea level. The area covers about 9.5 square kilometers. There are about 192 streets in Mason. The region was founded in 1861. The postal codes are 76856. The dialing code is 325. Mason is city in and county seat of Mason County, Texas, United States. Among other things, Mason has museums and schools. More information at www.mason.tx.citygovt.org.