What happened in 1803 that nearly doubled the size of the united states? a. president jefferson purchased the louisiana territory from france. b. england lost the war of 1812 and returned louisiana and texas to the u. s. c. the french withdrew from north america and gave all their territorial holdings to the u. s. d. the signing of the treaty of san ildefonso. e. the u. s. army defeated spanish troops in new spain and gained texas.