The Census Bureau figures show that Hispanics account for 36 percent of the total population in the nation 's five largest counties : 9.1 million of the 25.4 million people who live in Los Angeles , Cook County , Harris County , Tex . -LRB- Houston -RRB- , Maricopa County , Ariz. -LRB- Phoenix -RRB- and Orange County , Calif. .