Original: Nevada is notable for being one of only two states to significantly expand its borders after admission to the Union . Nevada achieved its current southern boundaries on May 5 , 1866 , when it absorbed the portion of Pah-Ute County in the Arizona Territory west of the Colorado River , essentially all of present day Nevada south of the 37th parallel .
Simplified: Later , on May 5 , 1866 , Nevada got its current borders because the Pah-Ute County in Arizona was taken as part of Nevada .