Question

which event doubled the size of the united states in the 1800s?
mexican - american war
annexation of texas
revolutionary war
louisiana purchase

Explanation:

The Revolutionary War established U.S. independence but did not expand its territory to double its size. The annexation of Texas added only one state-sized territory, and the Mexican-American War added territory but did not double the nation's size. The 1803 Louisiana Purchase from France added approximately 828,000 square miles, effectively doubling the area of the existing United States at that time.

Answer:

Louisiana Purchase