Yosemite National Park, Calif. ? Anthony Frost was just 200 feet from the summit of Half Dome when he lost his nerve. Then he almost lost his lunch.

“My heart was pounding. My boots started slipping and that kind of spooked me,” Frost, a teacher from Bakersfield, said after carefully backing down Half Dome’s cable route to level ground. “When I looked up, I started losing my equilibrium. It feels like you’re falling when you’re standing still. … I’m amazed I made it halfway.”

Half Dome is the 8,842-foot granite monolith that stands at the head of Yosemite Valley. Its sheer northwest face and smoothly curved shoulders are recognized around the world as the symbol of Yosemite National Park. Climbing to Half Dome’s summit is a popular 130-year-old tradition.

The park maintains steel cables that enable intrepid hikers to climb the last 900 feet of the route over a 45-degree pitch of slick granite — a slope too steep to climb without assistance. The trail can be an acrophobe’s worst nightmare. It helps to bring work gloves, shoes with good traction, and a good deal of brawn.

Conquering Half Dome

In 1868, about 15 years after the first tourists began arriving in Yosemite Valley, geologist Josiah Whitney surveyed the area. In his report to the state of California he wrote, “Half Dome was perfectly inaccessible, being probably the only one of all the prominent points about Yosemite which has never been and will never be trodden by human foot.”

His statement remained true for just seven years. On Oct. 12, 1875, George Anderson became the first man to make it to the top. According to an account in naturalist John Muir’s book, “The Yosemite,” Anderson, “an indomitable Scotchman,” hiked to the Saddle, an area between a small dome and the eastern shoulder of Half Dome.

Picking up at a point where others had failed, he “resolutely drilled his way to the top, inserting eyebolts five to six feet apart, and making his rope fast to each in succession, resting his feet on the last bolt while he drilled a hole for the next above. The whole work was accomplished in a few days.”

Anderson’s fixed ropes were eventually ripped off the mountain by avalanches. In 1919, the Sierra Club paid for the installation of the first set of permanent cables.

The present cables are raised waist-high, attached to metal pipes set in the rock. To protect from winter storms, the park takes down the support poles each autumn and puts them up again in the spring.

Don’t look down

On a warm and sunny day in June, Jenny Owens, 21, of Salinas, and her mother, Julie Rodgers, of Prunedale, arrived at the base cables after an 8.2-mile hike from the Happy Isles trailhead. They took a look at the steep route and then paused to ask for God’s help.

“We said a little prayer for courage and strength and safety,” Owens said.

“There were parts where it wasn’t so bad and there were parts where I was like ‘Oh (expletive).’ If you’re afraid of heights, don’t look down. Hold on tight and take one step at a time. It was the most challenging thing I’ve ever had to do,” she said.

Occasionally a hiker is overcome by a fear of heights and is unable to proceed in either direction.

“Oh, people ‘freeze’ on the cables all the time,” said Jim Snyder, the park’s historian. “They usually wait out their nerve or have a friend guide them. Sometimes they have no trouble going up but they have trouble going down so they go down backwards,” as if descending a ladder.

Reaching the summit

Each year thousands of hikers stand on Half Dome’s 13-acre summit. The park doesn’t keep official numbers but Snyder remembers one particularly crowded day. “On Memorial Day in 1972, more than 700 people went up. It was horrendous,” he said.

On the summit, most hikers linger for an hour or so, taking in the spectacular views of Yosemite Valley, nearly a mile below to the west, and the High Sierra to the east. Many use their cell phones to announce their conquest to family and friends. Others lie down on their bellies and crawl to the edge for a better look over the precipice.

Beware of bad weather

Despite its popularity, accidents on Half Dome are rare. When they do happen, it’s usually because of bad weather. Signs along the trail warn hikers to turn back at the first sign of a thunderstorm.

“Let’s face it, that’s the world’s biggest lightning rod. There have been two or three deaths” from lightning strikes, Snyder said.

Most accidents, however, occur when hikers with weary legs slip and fall on the trail back down to the valley.

Several decades ago a threatening storm forced Ray Bierl and his father to abandon an attempt to reach the summit. A few weeks ago, the 61-year-old musician from Oakland returned alone to fulfill a 40-year dream.

“When I was at the top I thought, man, this is the scariest thing I’ve ever done. I didn’t like the idea that if I let go I was going to die,” he said. “But now that I did it, I want to come back — and bring my friends.”