Swamped by weekend crowds of people tired of being cooped up in beautiful spring weather by shelter-in-place orders, several Bay Area parks announced Sunday that they were closing — or are giving it strong consideration.

Marin County took what may have been the most drastic measure, ordering all parks in the county closed, from 18,000 acres of county-managed lands to popular state and federal sites, including Point Reyes National Seashore, Muir Woods National Monument and Mount Tamalpais State Park.

Marin County Sheriff’s Office Sgt. Brenton Schneider said the large numbers of people were “creating unsafe conditions for employees” at local businesses who were “fearful about all the close contact that they’re witnessing.” The sweeping closure order, which also includes the Marin Headlands, Marin Municipal Water District lands and city parks, was issued by the county’s Department of Health and Human Services.

Meanwhile, officials in the East Bay were considering closing or severely restricting access at parks there after a similar weekend of jam-packed roads and parking lots, closed public restrooms and overwhelmed parks staff.

“Visitation is insane,” said Bob Doyle, general manager of the East Bay Regional Parks District. “In my 45 years of park work, I’ve never seen these type of crowds, not ever. People are desperate to get outside.”

In San Francisco, a spokesperson for the Recreation and Park Department said the parks would remain open, though it was clear that shelter-in-place orders were being tested, if not outright ignored.

At 10:30 Sunday morning, an AlertSF text went out advising people to “stay home, save lives.” The alert said it was OK to go for walks or bike rides but said to avoid crowds and stay 6 feet away from other people. That didn’t seem to reach those going up and down the Lyon Street steps in Cow Hollow. The popular outdoor StairMaster was as crowded as it always is on a Sunday morning.

“I’m trying to maintain a distance, but I feel like it is important to keep your immune system strong and keep exercising,” said Kai Pitoy, an accountant who lives in the Marina. “For our sanity, you have to get out.”

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The attempt to maintain sanity through exercise and fresh air is what seems to have put all the drivers on the roads to beaches in the Marin Headlands. Robyn Graham, 30, of Half Moon Bay and Kara Quan-Montgomery, 33, of Richmond headed to Tennessee Valley for a hike.

“But it was slammed. There was no parking,” Quan-Montgomery said. So they headed for Fort Cronkhite, where they stood in the nearly full parking lot perusing a trail map.

“I just needed to get out,” Graham said. “A lot of people are going stir-crazy, and since they say you can get out and exercise, we came here.”

By 12:30, the lot at Rodeo Beach and the street-side parking was filled. A long line of cars headed slowly to the beach. Surfers bobbing in the waves did not seem worried about getting too close to one another and neither did the people walking on the sand.

“The beach is a place you can stay 6 feet away from each other. You can obey the social distancing rules,” said San Rafael’s Travis Lateefah, who had been sent home from Trinity College in Hartford, Conn.

Also at the beach after being sent home from college was Red Ongaro, who attends Purdue, in Lafayette, Ind.

“My family just wanted to come out to the beach and get some sunshine,” he said. “We were getting a little tired of staying inside.”

And at Stinson Beach, where the parking lot had already been closed to discourage crowds, street parking was jammed with cars parked along the shoulder. There was a long line for burgers and soft-serve ice cream at the Parkside Cafe, and nobody was maintaining 6 feet of distance in the line at the window.

Small signs on bright green paper had been affixed to park signs, reading, “If you don’t live here, go home and stay there. You are putting us in danger. Shelter in place means stay at home.”

Several days of it had pushed people to the brink. Seven Bay Area counties, including Marin, announced shelter-in-place orders Monday, which have since been embraced by other counties and the state.

The biggest problem in the East Bay parks, according to General Manager Doyle, is that friends are arriving separately, filling parking lots, then gathering in groups of eight or 12 and turning a walk into a social event.

A tour of 22 trailheads and parks on Saturday revealed packed parking lots, illegally parked cars, blocked gates and access roads, and restrooms closed after visitors stole the toilet paper and hand sanitizer.

At Tilden Regional Park, cars filled the lot at Inspiration Point, which is typical for a weekend, but also were parked illegally along the shoulders of Wildcat Canyon Road, partially blocking the lanes. Nearby, at the Lake Anza Overlook, somebody moved a barrier in order to park illegally. Another vehicle was parked across a pedestrian crossing.

It was like that in many parts of the Bay Area, according to reports from rangers. In West Marin, a huge sign was posted along an access road that read “Go Home.” Residents of the area reported jammed roads anyway, including Sir Francis Drake and Highway 1.

In San Francisco, a personal trainer set up a gym on Outer Broadway, at the top of the Lyon Street steps, with free weights, a bench for doing crunches and a bar for doing pull-ups. She was putting her client through a circuit that included a lap down and up the steps, followed by a series at the machines.

Susannah Raub went for a run in Golden Gate Park on Saturday and found it too crowded, so she came to the Lyon Street steps on Sunday morning. “I’m staying inside except to come out and do these steps,” she said.

The advocacy group Walk San Francisco has started an online petition to make John F. Kennedy Drive, the main east-west thoroughfare through the park, car-free every day while the shelter-in-place directive is in effect. Raub would be happy to sign it.

“Close JFK to cars,” she said before starting up the stairs.

At the bottom of the steps, above Green Street, Raub was able to maintain a courteous social distancing, but it tended to break down on the steps themselves, where faster climbers were breathing down the neck of climbers ahead of them.

“It’s tricky,” Raube said. “I try to leave space, especially if it looks like someone is faster than me.” Only a railing separates the people coming down from those going up, and there is plenty of used carbon dioxide being huffed out by people moving in either direction.

“There is a brief moment where you are near somebody, but you have to be able to exercise and the gyms are closed,” said Steve Polevoio. “We try not to breathe or cough on anybody and hopefully they are showing us the same respect.”

Sam Whiting, Michael Cabanatuan and Tom Stienstera are San Francisco Chronicle staff writers. Email: swhiting@sfchronicle.com, mcabanatuan@sfchronicle.com, tstienstra@sfchronicle.com Twitter: @ctuan, @StienstraTom