Final answer:
Texas, also known as the Lone Star Republic, was an independent country before becoming the 28th state of the United States in 1845.
Step-by-step explanation:
Texas was an independent country prior to joining the United States. Known as the Lone Star Republic or the Republic of Texas, it existed from 1836 to 1846 following the Texas Revolution against Mexico. Texas joined the United States in 1845 after the Texan government, led by President Sam Houston, secured a deal with U.S. President James K. Polk, facilitating the annexation of Texas as a state.
As a contrast, Alaska was purchased from Russia and was recognized as a U.S. territory in 1912, while Florida was acquired through the Adams-Onís Treaty from Spain and became a U.S. state in 1845 as well. As for Montana, it was part of the Louisiana Purchase and later became a state without any period of recognized independence.