Celebrating its 100th anniversary, Save the Redwoods League is offering free passes at 47 redwood state parks on the second Saturday of each month in 2018.

A total of 16,000 passes, which cover day-use admission and parking fees, are available this year.

The passes for Saturday have sold out, and passes for the next second Saturday on Feb. 10 will be available online at www.savetheredwoods.org starting at 8 a.m. on MondayJanuary 15.

Eight state parks in Sonoma County are participating in the giveaway supported by the league and Oracle, the computer technology corporation founded in 1977 and headquartered in Redwood City.

Eleven parks in Mendocino County and four in Napa County are also participating, along with parks from Del Norte to Monterey counties.

“People come from around the world to walk among California’s ancient redwoods,” said Sam Hodder, president and CEO of the league.

The 17,500-member league has preserved more than 200,000 acres of redwood forest and helped establish 66 parks.

Lisa Mangat, California state park director, said her agency and the league “work through our state parks to support the health, inspiration and education of all Californians.”

More than 30 million people visit a redwood park each year, the league says.

You can reach Staff Writer Guy Kovner at 707-521-5457 or guy.kovner@pressdemocrat.com. On Twitter @guykovner.