If approved, the sales tax increase would raise approximately $60 million each year for the county's General Fund and would be in effect for 10 years.
In a four-to-one vote, the Board of Supervisors Tuesday approved an ordinance that will place the tax measure on the Nov. 6 ballot.
Supervisor Don Horsely, who co-sponsored the measure with Board president Adrienne Tissier, said that the money raised by the new tax would be used to preserve vital public safety and health care services that have been severely cut due to countywide budget shortfalls, a sluggish economy and dwindling funding from the state.
Looming additional cuts would be devastating to low-income children, fire protection in unincorporated areas, and emergency room services at Seton Medical Center in Daly City, Horsely said.
"I think this is a very vital time for us to make the case to the voters," he said.
Tissier warned that the great quality of life enjoyed by San Mateo County residents was beginning to erode, and that funds raised by an increased sales tax would help to maintain the parks and programs that make the county such a wonderful place to live.
"We're going to have to take it upon ourselves to provide that funding," she said.
Supervisor Dave Pine, who cast the one dissenting vote against the measure, said that a half-cent sales tax would hurt local businesses and disproportionately impact low-income residents.
Pine suggested that a one-quarter cent sales tax would be more likely to pass, and that -- combined with other growing revenues -- could prevent further cuts to vital services.
Supervisor Carole Groom, who said this was "the single most difficult issue and vote" that she had faced in her career as an elected official, voted to support the measure despite having opposed tax measures in the past.
"These are different times and we have made some very serious and severe cuts in this county," she said.
The tax measure will need a simple majority to pass.