Which of these states made a treaty as a sovereign nation to join the United States before becoming a state?

Texas declared independence from Mexico on March 2, 1836. After the victory at the Battle of San Jacinto on April 21,1836 , a peace treaty with Mexico secured Texas' tenuous independence from Mexico.

Sam Houston became the first President of the Republic of Texas on October 22, 1836. Many Texans wanted to join the United States. The Republic of Texas, as a sovereign nation, signed the Treaty of Annexation - Texas on April, 12, 1844. This treaty paved the way for Texas statehood. Congress passed a bill to authorize annexation on Feb. 28, 1845. On March 1,1845 President John Tyler signed the bill. Texas became the 28th state on December 29, 1845.

"In the Texas presidential race of 1844, Vice President Edward Burleson faced Secretary of State Anson Jones, who had the support of Houston. Jones won by a large vote. After he was inaugurated on December 9, he launched a policy of economy, peaceful relations with the Indians, and a nonaggressive policy toward Mexico. As his administration also tackled the issue of annexation, Jones earned the sobriquet "Architect of Annexation." .... President Tyler had indicated in October that he wanted to open discussions leading to the annexation of Texas by treaty. An annexation treaty was completed on April 12, 1844, and signed by Secretary of State John C. Calhoun, Isaac Van Zandt, and Van Zandt's assistant, J. Pinckney Henderson." The Handbook of Texas