Orange County’s unadjusted unemployment rate dropped to 2.4% in September from a revised 3.0% in August and below the year-ago estimate of 2.8%, according to the state Employment Development Department.

California’s unemployment rate was 3.5% and the U.S.’s was 3.3%. The most recent numbers for the county, state and U.S. aren’t seasonally adjusted. OC’s lowest-ever unemployment rate was 2.2% in December 1999.

OC nonfarm employment increased by 8,200 jobs to 1.67 million. Eight of its 11 sectors reported increases in September while three sectors reported declines.

The biggest increase was 8,400 in the government sector due to teachers returning to their classrooms after the summer break. Professional and business services added 1,900 jobs, led by temporary help firms.

Leisure and hospitality recorded the largest employment decline with the loss of 3,300 jobs, led by accommodation and food services.

About 17.5 million people worked in California outside of agriculture in September, up about 21,300 from August and 320,000 from a year earlier.

Statewide, eight of 11 industry sectors added jobs month-over-month, led by professional and business services, up 12,700, and manufacturing and educational and health services, which each were up 4,100 jobs. The category of other services had the biggest decline, 2,000.

People receiving unemployment benefits declined to 281,060 in September from 309,691 in August. The September number last year was 284,790.