Question: What president of the United States signed the Treaty of 1818, which gave United States of America the Pembina Region?

Context paragraphs:
Treaty of Manila (1946): The Treaty of Manila of 1946, formally the Treaty of General Relations and Protocol, is a treaty of general relations signed on none }} in Manila, the capital city of the Philippines.  Parties to the treaty were the United States of America and the Republic of the Philippines.  The United States granted the Philippines full independence, and the treaty provided for the recognition of that independence.  The treaty was signed by High Commissioner Paul V. McNutt as a representative of the United States and President Manuel Roxas representing the Philippines.

U.S.–Japan Status of Forces Agreement: U.S.–Japan Status of Forces Agreement (formally, the "Agreement under Article VI of the Treaty of Mutual Cooperation and Security between Japan and the United States of America, Regarding Facilities and Areas and the Status of United States Armed Forces in Japan") is an agreement between Japan and the United States signed on 19 January 1960 in Washington, the same day as the revised U.S.-Japan Security Treaty.  It is a status of forces agreement (SOFA) as stipulated in article VI of that treaty, which referred to "a separate agreement" governing the "use of [...] facilities and areas [granted to the U.S.] as well as the status of United States armed forces in Japan".  It replaced the earlier "U.S.-Japan Administrative Agreement" that governed such issues under the original 1951 security treaty.

Treaty of Cession of Manu'a: The Treaty of Cession of Manuʻa, also known as the Deed of Cession of Manuʻa, was a treaty between Tui Manuʻa Elisala and the United States signed on 16 July 1904 that ceded the islands of Manuʻa to the United States, which now forms part of American Samoa.  It was ratified by the United States Congress by the Ratification Act of 1929.

Treaty of Cession of Tutuila: The Treaty of Cession of Tutuila, also known as the Deed of Cession of Tutuila, was a treaty between several chiefs of the island of Tutuila and the United States signed on 17 April 1900, whereby the chiefs swore allegiance to, and ceded the island of Tutuila to, the United States, which now forms part of American Samoa.  It was ratified by the United States Congress by the Ratification Act of 1929.

Treaty of 1818: The Convention respecting fisheries, boundary and the restoration of slaves between the United States of America and the United Kingdom of Great Britain and Ireland, also known as the London Convention, Anglo-American Convention of 1818, Convention of 1818, or simply the Treaty of 1818, was an international treaty signed in 1818 between those parties.  Signed during the presidency of James Monroe, it resolved standing boundary issues between the two nations.  The treaty allowed for joint occupation and settlement of the Oregon Country, known to the British and in Canadian history as the Columbia District of the Hudson's Bay Company, and including the southern portion of its sister district New Caledonia.

Cuban–American Treaty of Relations (1903): The 1903 Cuban–American Treaty of Relations was a treaty between the Republic of Cuba and the United States signed on May 22, 1903.  The treaty contemplated leases of Guantánamo Bay; one such lease had been executed earlier in the year in February 1903, and a second lease was executed later in the year in July 1903.

Treaty of St. Mary's: The Treaty of St. Mary's (also known as the Treaty with the Miami, 1818) was signed on October 6, 1818, at Saint Mary's, Ohio, between representatives of the United States and the Miami tribe and others living in their territory.  The accord contained seven articles.  Based on the terms of the accord, the Miami ceded territories beginning at the Wabash River, subsequently known as the New Purchase, to the United States.  In another tenet of the accord, the United States agreed to pay the Miami a perpetual annuity of fifteen thousand dollars.  Moreover, the United States agreed to construct one gristmill and one sawmill, as well as provide one blacksmith, one gunsmith, and agricultural implements.  The Miami would also be provided one hundred and sixty bushels of salt annually.

Pembina Region: The Pembina Region ( ), also referred to as the Pembina District and Pembina Department, is the historic name of an unorganized territory of land that was ceded to the United States.  The area included parts of what became North Dakota, and a portion of central eastern to northeastern South Dakota.  The eastern boundary was the Red River, and included the Pembina River area.  The region was formerly part of British Rupert's Land and the Red River Colony (controlled by the Hudson's Bay Company), that encompassed an area then known as the Assiniboia District, from 1763 to the signing of the Treaty of 1818.  The treaty transferred the region that was south of the 49th parallel from the British to the United States.

Webster–Ashburton Treaty: The Webster–Ashburton Treaty, signed August 9, 1842, was a treaty resolving several border issues between the United States and the British North American colonies (i.e. the region that became Canada).  Signed under John Tyler's presidency, it resolved the Aroostook War, a nonviolent dispute over the location of the Maine–New Brunswick border.  It established the border between Lake Superior and the Lake of the Woods, originally defined in the Treaty of Paris in 1783, reaffirmed the location of the border (at the 49th parallel) in the westward frontier up to the Rocky Mountains defined in the Treaty of 1818, defined seven crimes subject to extradition, called for a final end to the slave trade on the high seas, and agreed to shared use of the Great Lakes.  The treaty retroactively confirmed the southern boundary of Quebec that had been marked by stone monuments by land surveyors John Collins and Thomas Valentine in 1771–3.  It had been intended to be at 45 degrees north latitude, but is in some places nearly a half mile north of the parallel.

Morden, Manitoba: Morden is a city located in the Pembina Valley region of southern Manitoba, Canada near the United States border.  It is about 11 km west of the neighbouring city of Winkler.  Morden, which is surrounded by the Rural Municipality of Stanley, is the second largest city in Canada's Pembina Valley region.  The city is located south of the Winnipeg Capital Region.  The communities of Morden and Winkler are often referred to as Manitoba's Twin Cities, due to their extremely close proximity, shared services, and economic ties.  According to Statistics Canada, the city had a population of 8,668 in 2016.

Supporting paragraphs: Pembina Region Treaty of 1818
Answer: James Monroe