The Mat-Su rivers and lakes are home to the spawning grounds of chinook, coho, sockeye, pink, and chum salmon. The area is home to 31 state parks and campgrounds. The 23,000-square-mile (60,000 km 2) Matanuska-Susitna Borough (the Alaskan equivalent of a county) governs the Mat-Su Valley. According to the 2010 Census, the borough's population is 88,995, a 50% increase since 2000. The Mat-Su Valley was originally inhabited by Athabaskan people and was explored by Russians in 1818.