List of National Border Changes From 1815 To 1914 - North America

North America

• 1815 - With the end of the War of 1812, the borders between British North America and the United States of America return to their pre-war borders.
• 1818 - The borders between British North America and the United States during the Treaty of 1818 establishing the 49th parallel north west of the Lake of the Woods. The Oregon Country is established by both the United States and Britain which hold it in union.
• 1821 - July 10 - The borders between Oregon Country and Mexico are changed as well as Spain ceding Florida after Spain ratifies the Adams-Onís Treaty which was drafted in 1819.
• 1836 - March 2 - The Republic of Texas is declared after it separates from Mexico, but its western territory remains disputed with Mexico.
• 1845 - December 29 - Texas is annexed by the United States
• 1846 - June 18 - The Oregon Treaty ends the sharing of the Oregon Country, with the territory north of the 49th parallel going to British Columbia and the territory south of the 49th parallel becoming an unorganized territory of the United States.
• 1846 - 1848 - Mexican-American War occurs and ends with the Treaty of Guadalupe Hidalgo in which Mexico cedes territories consisting of all of present-day California, Nevada, Utah, most of Arizona and portions of Colorado, New Mexico, and Wyoming.
• 1853 - December 30 - The Gadsden Purchase gives territory from Mexico to the United States, establishing the present-day border with Mexico.
• 1861 - 1865 - American Civil War. After the Confederate States of America (CSA) is founded in February of the year, war breaks out in April, between the Unionists and the Confederates of the CSA, as well as rebel CSA-supporting governments in some southern states. The war ends with the CSA being defeated and annexed by the United States.
• 1867 - July 1 - Canada is created after the British North American provinces of Ontario, Quebec, New Brunswick, and Nova Scotia join during the Canadian Confederation. October 11 - The United States annexes Alaska after it is sold from Russia in the Alaska purchase.
• 1870 - July 15 - The United Kingdom formal cedes the North-Western Territory and Rupert's Land and its interests there to Canada, and the province of Manitoba joins Canada.
• 1871 - July 20 - the British colony of British Columbia joins Canada.
• 1873 - July 1 - Prince Edward Island joins Canada.
• 1880 - September 1 - The United Kingdom cedes its remaining Arctic Islands to Canada.
• 1903 - October 20 - The Hay-Herbert Treaty is signed by Britain and the United States which settles the Alaska boundary dispute between Canada and the United States, which gives the United States more territory.