The history of Texas as part of the Unite States began in 1845, but settlement of the region dates back to the end of the Upper Paleolithic Period, around 10,000 BC. Its history has been shaped by being part of six independent countries: Spain, France, Mexico, the Republic of Texas, the Confederate States of America, and the United States of America. Starting in the 1820s, American and European immigrants began arriving in the area; joined by Hispanic Tejanos they revolted against Mexico in 1836 and defeated an invasion army. After a decade as an independent country, Texas joined the Union (the United States) in 1845. The western frontier state was characterized by large-scale cattle ranching and cotton farming. In the 20th century, it grew rapidly, becoming the second largest state in population 1994, and became economically highly diversified, with a growing base in high technology. The state has been shaped by the interactions of Southern, Spanish, Tejano, Native American, African American, and German Texan cultures.