Yosemite National Park has long been known as a place with stunning waterfalls, dramatic rock formations, and frustrating weekend crowds. But all that is changing.

The waterfalls and rocks are still there. A lot of the people aren't.

The number of visitors to Yosemite, in northern California, hit a 16-year low last year, according to statistics made public last week. Nobody knows exactly why attendance has been falling for a decade, although park officials point to busy families, video games, and a series of natural disasters.

The 3.36 million visitors in 2006 were nearly 20 percent fewer than Yosemite's peak 10 years ago, even though California added seven million people - equivalent to the combined populations of Chicago, Houston and Philadelphia - in that span.

"The traffic is less. I'm not seeing the backups that we used to see," said Scott Gediman, a ranger who has worked in Yosemite since 1996. "You don't see crowds of people as much."

Key holidays such as Memorial Day and Labor Day weekends and the Fourth of July remain busy. But increasingly, very crowded days are the exception. A few minutes' walk up a trail from Yosemite Valley can mean solitude.

"You can go out on an August day on a Tuesday afternoon and it is more peaceful and quiet now, which is wonderful," Gediman said. "But we'd like people, if they haven't been here in a couple of years, to come back."

Park officials and business leaders from neighboring counties have plenty of theories about the decline. Among them: A series of natural disasters - including a flood in 1997 and a 2006 rock slide that closed one of the park's main roads, Highway 140, from April to August - has scared visitors away.

Also, some suggest, many parents are working longer hours and can't get away from e-mail, cell-phone calls, and the pressures of the office for extended periods. In addition, children have more entertainment options than they used to.

"We certainly want parks to be relevant to young people today and to pass on the preservation ethic," Gediman said, "but there is a different entertainment ethic. Half Dome is competing now with PlayStation and Xbox."

The decline worries neighboring counties.

Mariposa County, on the park's western edge, draws 60 percent of its discretionary budget from hotel taxes. Business leaders there fear that although Highway 140 is open to vehicles less than 28 feet long, work to repair the road after the rock slide could send several hundred tour buses on another route or out of the park entirely, said Leroy Radanovich, tourism coordinator for the Mariposa County Visitor's Bureau.

He said that in addition to youths' added pursuits, aging baby boomers in many cases preferred luxury vacations to camping and backpacking.

"In the early 1970s, you had to stand in line to get a wilderness permit," Radanovich said. "Today there's no problem. The high country of Yosemite is virtually empty."

The park is facing financial consequences as well.

In the 1990s, the entrance fee rose to $20 a car from $5. Most of that money goes to maintaining Yosemite's roads, restrooms and other facilities. The park's $22 million operating budget comes from Congress, but lower attendance means less money for capital improvements.

In recent years, with significant help from donations, the park has renovated the visitor areas around Yosemite Falls, built new boardwalks on its famed meadows, and built a new visitors' center.

But other improvements have been mired in years of lawsuits by several small environmental groups. For example, Yosemite Lodge lost roughly half its 500 rooms in the 1997 flood, and they have not been rebuilt. Nor have roughly 300 campsites wrecked by the flood, cutting the number of overnight campsites in Yosemite Valley to 500.

Attendance at other big parks in the West, such as Yellowstone, also is down. Attendance at all 390 national parks declined from 287 million in 1999 to 273 million in 2005, about 5 percent.

Some Yosemite visitors are quite pleased by the trend.

Steve and Terri Bicknell of San Jose, Calif., and their daughters, Kelli, 11, and Ashley, 19, plan a camping trip in May.

"I'm glad the attendance is down," Steve Bicknell said with a laugh. "That's good news for me. It will make us want to go more."