Maine was originally part of Massachusetts. It was included in the Charter of New England in 1620 and the Charter of Massachusetts Bay in 1629; the latter became the Constitution of the Massachusetts Bay Colony, predecessor to the Commonwealth of Massachusetts. In 1819, Massachusetts agreed to allow its district of Maine to petition for statehood. Maine was admitted to the Union as a separate state on March 15, 1820, as the 23rd state. The state's boundary with Canada was not formally established until the Webster-Ashburton Treaty of 1842, when Maine assumed generally the same boundary as the present state.