WASHINGTON – Americans stepped up their spending at retail businesses in September, reflecting higher consumer confidence. The increase was driven by another strong month of auto sales and the release of the iPhone5.

Retail sales rose 1.1 percent last month to a seasonally adjusted $412.9 billion, the Commerce Department said Monday. That followed a 1.2 percent increase in August, which was revised slightly higher. Both were the largest gains since October 2010.

Sales rose last month in most major categories. Electronics and appliances surged 4.5 percent, in part because of iPhone sales. Sales at auto dealers increased 1.3 percent. Building materials and garden supplies, furniture and clothing sales all gained, too.