Development of resorts also proliferated on rivers and high mountain valleys. The Seven Oaks Camp was established on the banks of the Santa Ana River in 1890, and resorts also grew up at Crestline and Running Springs in higher regions of the San Bernardino Mountains. Snow in the San Bernardinos was seen as an obstacle before the 1920s and practically shut down recreation in the winter. However, more and more Southern Californians braved the dangers of winter travel in the mountains, and Lake Arrowhead became a sought-after winter destination by the 1930s.