Attained when the forty-ninth parallel was extended to the pacific?

The statement refers to the Oregon Treaty of 1846, which established the boundary between the United States and British North America at the forty-ninth parallel, extending it all the way to the Pacific Ocean. This agreement resolved the Oregon boundary dispute and facilitated the U.S. expansion into the Pacific Northwest. The treaty was significant in shaping the territorial claims and borders of the United States in the mid-19th century.