The Interior Department on Tuesday said Yosemite, Grand Canyon, Yellowstone and 144 other national parks would offer free admission on three weekends this summer: June 20-21, July 18-19 and Aug. 15-16.
At Yosemite, that can save $20 per car, or $10 per person for those who arrive by foot, bicycle or motorcycle.
"During these tough economic times, our national parks provide opportunities for affordable vacations for families," Interior Secretary Ken Salazar said at a news conference at Cuyahoga Valley National Park in Ohio.
"I encourage everyone to visit one of our nation's crown jewels this summer and especially to take advantage of the three free-admission weekends."
Besides free entry, some concessionaires will give away $5 vouchers, tours, boat rides, shopping bags or other extras. But don't expect to camp for free; regular camping fees will still apply.
The National Park Service typically waives entry fees on National Public Lands Day (the last Saturday in September) and for military service people and veterans on Veterans Day, Nov. 11, said spokeswoman Kathy Kupper. She said she could not recall another time in her 20-plus years with the park service that fees had been waived for entire weekends for the public.
Most Americans live less than a day's drive from a national park, Salazar said. Last year, national parks attracted more than 275 million visits, generating an estimated $10.6 billion for local economies and supporting more than 213,000 jobs, he said.
Many of the system's 391 parks never charge an entry fee.