No one knew precisely how much land Louisiana contained, or where its exact boundaries were. It was settled by the French in the early 18th century, but secretly ceded to Spain in 1763. In 1764, Great Britain acquired all of Louisiana east of the Mississippi in a settlement following the Seven Years War. In 1783 the Treaty of Paris, between Great Britain and the Thirteen Colonies, concluded the American Revolution, and ceded the British portion of Louisiana to the new, free and sovereign United States of America. It also defined the boundary between the U.S., Spain's Louisiana territory, and Canada, but the description of that line, and the map on which it was based, were so vague that overlapping claims were inevitable.
The treaty specified that the boundary would extend due west from the northwestern point of Lake of the Woods, to the Mississippi River. That point, where the boundaries of Ontario, Manitoba, and Minnesota now intersect, was soon determined to be situated at 49 degrees, 37 minutes north latitude. However, the map used by the treaty negotiators placed the source of the Mississippi more than 150 miles north of its actual location – Lake Itasca in northwestern Minnesota – which was finally pinpointed in 1832, and confirmed in 1836.
The misunderstanding about the location of the Mississippi's source was relatively unimportant until the United States acquired the rest of Louisiana in 1803.1 Then, it raised questions not only about land ownership, as reference to the accompanying map will show, but also about "rights" to trade with Louisiana's indigenous residents, and freedom of commercial travel, especially via water routes. People, as such, were not part of the equation. So, with or without official sanction, but certainly with the interests of his country in mind, Meriwether Lewis inserted himself into the issue along with the fate of the expedition under his command.
The larger part of the western boundary controversy was partially resolved in 1818, when Great Britain and the U.S. agreed on the 49th parallel, about 43 miles south of that northwestern point of Lake of the Woods, as the boundary westward as far as the Rocky Mountains. The boundary from the crest of the Rockies to Puget Sound remained in dispute for nearly thirty years longer, with the British demanding to keep the entire Columbia River, and American expansionists reaching for the southern tip of Alaska, at 54 degrees, 40 minutes north.2 Compromise was reached in the Oregon Treaty of 1846, which extended the boundary along the 49th parallel. Once again, language confounded intent, and disagreement over the ownership of the San Juan Islands led to the "Pig War" of 1859, and ultimately, in 1872, to a need to submit the dispute to arbitration by William I of Germany.
Meanwhile, Indian people such as the Blackfeet called the 49th parallel a "medicine line," because it seemed to be a mysterious, invisible barrier. When a person crossed it, some rules changed. Different political allegiances applied; soldiers and police couldn't step over it.
It took 142 years to resolve all the basic boundary issues raised by the Treaty of Paris, and to turn an imaginary and largely artificial line into a visible feature on the landscape. The Boundary Treaty of 1925 finally clarified the political distinctions between Canadian land and American land. It also established a permanent International Boundary Commission to supervise boundary maintenance on a year-round basis. Today, surveyed and marked, the line is defined on the ground by monuments and, where necessary, a 20-foot swath, or "vista," cut through brush and trees. Yet new issues, particularly relating to water rights and environmental issues, continue to arise.
1. Jay's Treaty of 1794, which was the outcome of efforts by Congress's special envoy John Jay (1745-1829) to re-negotiate some of the original terms in the Treaty of Paris, did not include the western boundary issue.
2. The Democratic Party elected President James Polk in 1844 with the fiery slogan, "Fifty-four forty or fight!" Their goal was to gain exclusive U.S. control of the "Oregon Territory" between 41° and 54° 40' North Latitude and west of the Divide. Other international issues diluted the administration's energies, and the Oregon Treaty of 1844 was the compromise.