Complex sentence: In 1812 the Pacific Fur Company founded a rival post, known as Fort Spokane, located 35 miles west at the confluence of the Spokane and Columbia Rivers, and declared to the native peoples of the region their readiness to compete for furs.
Split into simpler sentences: In 1812 the Pacific Fur Company founded a rival post, known as Fort Spokane, located 35 miles west at the confluence of the Spokane and Columbia Rivers. It announced to the native peoples of the region their readiness to compete for furs.