In an effort to resolve disputes over hunting territory, in 1858 the Chippewas and Dakotas, with the assistance of U.S. negotiators, agreed to the "Sweet Corn Treaty", defining their respective lands. The Chippewa lands were about 11,000,000 acres. The Dakota Territory became an organized territory on March 2, 1861. Two years later, the federal government, pressured by people who wished to settle there, entered into negotiations with the Pembina and the Red Lake Chippewas. One of the representatives of the Pembina Chippewa, who lived west of the Red River, was Little Shell. The U.S. Government asked the Chippewas to cede about 9 million acres. In 1863, the United States signed The Old Crossing Treaty with the Red Lake and Pembina Bands of Chippewa who ceded several thousand acres of Indian lands near the Red River of the North to the United States government in exchange for a nominal amount of money to be paid to the Chippewa. Chief Little Shell signed for the Pembina band. By 1875, the Government had compelled a substantial part of the Pembinas, on threat of loss of their annuities from the 1863 cession, to move from the unceded portion to the White Earth reservation in Minnesota. The rest remained in the area of Turtle Mountain. In 1882, the Turtle Mountain Reservation of about 460,000 acres was established. Two years later, the area was reduced to about 46,000 acres. The federal government did not include in its calculations those Chippewas who periodically crossed over to Canada for hunting, nor the Metis, the offspring of a Chippewas mother and an English or French fur trader. The reservation was entirely too small. By 1892 McCumber was a federal commissioner. He and others met with Chief Little Shell who wanted to retain more land than acceptable to the commission, and refused to accept the terms, including the government's offer of 10 cents an acre for 10 million acres of prime farming land. He walked out of the negotiations in protest and never signed the subsequent McCumber Agreement. His people were left out of the settlement. Negotiations continued with a Council of 32" selected by the local federal agent, John Waugh. Although Little Shell traveled to Washington, D.C. to file a protest in Washington regarding the negotiations, the McCumber Agreement was accepted by Congress in 1904. The Turtle Mountain Band of Chippewas received $1,000,000 for the 9,000,000 acres they ceded.
Senator
McCumber was elected to the US Senate in 1899. McCumber was re-elected in 1905, 1911, and 1916 and served from March 4, 1899, to March 4, 1923. He was an unsuccessful candidate for renomination in 1922, having been defeated in the Republican primary by former governor Lynn Frazier. In the Senate, he was chairman of the Committee on Manufactures and a member of the Committee on Pensions, the Committee on Indian Affairs, the Committee on Transportation Routes to the Seaboard, and the Committee on Finance. In 1905, McCumber was an ardent advocate of a pure food law. One of his main legislative accomplishments was the Fordney–McCumber Tariff Act of 1922. In his position on the Pension Committee, he was part of the interrogation of Colonel W.S. Metcalfe on the alleged shooting of unarmed prisoners during the Philippine–American War, at the Battle of Caloocan, on February 10, 1899. Brigadier General Frederick Funston was accused of interfering with an investigation into the alleged shooting. Metcalfe denied the charges. McCumber was Woodrow Wilson's staunchest Republican supporter in the Senate for the League of Nations.
