The Oregon Territory originally included the modern states of Idaho, Washington, and Oregon. It was bounded by the Pacific Ocean to the west, California to the south, and the Rocky Mountains to the east. In the early 19th century, adventurous Americans began settling in the Oregon Territory to establish homes, farms, and towns, despite barriers like mountain ranges blocking passage to the western lands. The United States officially gained control of the Oregon Territory through a treaty with Britain in 1846.