Complex sentence: The California Gold Rush in the mid- 19th century dramatically increased travel by European-Americans in the area, causing competition for resources between the regional Paiute and Miwok and the miners and hangers on.
Split into simpler sentences: The California Gold Rush in the mid- 19th century dramatically increased travel by European-Americans in the area. This caused competition for resources between the regional Paiute and Miwok and the miners and hangers on.