The admission dates for later states were set by either the act of admission or a later resolution issued under that act, except for Ohio, whose date of admission was determined by act of Congress in 1953 as March 1, 1803, when its legislature first met because of a clerical error of omission—the original act omitted setting a date that the act took effect.[note 1]
This list does not account for the secession of 11 states during the American Civil War to form the Confederate States of America, the subsequent restoration of those states to representation in Congress (sometimes called "readmission") between 1866 and 1870, or the end of Reconstruction in those states. Since their secession was declared illegal by the U.S. Supreme Court in the case of Texas v. White, the Supreme Court, a branch of the federal government, does not give legal recognition to their having left the Union. The list also does not account for secessionist governments formed in two other states, as their Unionist governments generally remained in control.
^ abCongress recognized the state of Ohio on February 19, 1803 ("An act to provide for the due execution of the laws of theUnited States, within the state of Ohio", Seventh Congress, Session II, Chapter VII), but no formal date of statehood was set by the act of admission or a later resolution, as occurred with all other new states. On August 7, 1953, Congress passed a law retroactively setting the date of Ohio's statehood at March 1, 1803, the date when Ohio's first legislature convened.
^Although the Republic of California, also known as the Bear Flag Republic, was declared on June 14, 1846 by Anglo-American settlers in Sonoma, that lasted only for 26 days, and never achieved internal or external recognition.
^ abThe actual statehood proclamations for North and South Dakota were intentionally shuffled so it is unknown which state was admitted first. President Benjamin Harrison always refused to tell the order in which he had signed the two statehood bills. However, North Dakota's proclamation was published first in the "Statutes at Large", since it is first in alphabetical order.