Montana Before Statehood: A Land of Transformation. Following Lewis and Clark, fur trappers and traders were drawn to the area's abundant beaver pelts. They established trading posts and interacted with Native American tribes, further opening the region to outside influence. However, this also led to conflict and displacement of native populations. In 1846, the Oregon Treaty established the 49th parallel as the boundary between the United States and British North America, solidifying American control over the southern part of what is now Montana. This area was then incorporated into the sprawling Oregon Territory.