Lake Sonoma 50 is a 50-mile ultra marathon race held near Healdsburg, California. The course circumnavigates the Warm Springs arm of Lake Sonoma on hiking trails. It takes place annually on the second Saturday in April. The race was first run in 2008. In recent years it has become one of the most highly competitive ultra marathons in the United States.
References
Lake Sonoma 50 Wikipedia(Text) CC BY-SA