St. Mary's is a city located in the U.S. state of Alaska. It is within Kusilvak Census Area and the adjacent village of Andreafsky joined with St. Mary's in 1980. The total area is 50.2 square miles at 62°2′43″N 163°13′7″W. St. Mary's was incorporated on August 2, 1967. As of the census of 2010, there were 507 people living in the city. The population density was 10.86/sq mi. It had a population growth of 24.72 percent since 2000. St. Mary's recent job growth is negatively decreased by 0.74 percent. Estimated per capita income was $21,778. Zip code is 99658.