Now that he’s back at sea level, Kelso resident Patrick Gallaher is noticing the green. Saturday, the 43-year-old Wal-Mart pharmacist returned home from a three-week ascent to the top of Mount McKinley, the highest peak in North America and what some call the most difficult summit in the world.

“We’ve been looking at all that white for all those weeks, so everything looks greener. It takes something like that to appreciate it,” Gallaher said last weekend.

On May 8, he left his wife, Shelly, and two young daughters, ages 5 and 9, and flew to Anchorage, Alaska. Guided by three expert climbers from the American Alpine Institute, he and 11 others in his group began their snowy hike May 11 from a glacial airstrip in Denali National Park and Preserve.

“It was a heck of an adventure,” Gallaher said.

He’d been preparing for this for years. As an Eagle Scout, he enjoyed backpacking. He continued backpacking in college after serving four years in the Army. Then he read Jon Krakauer’s book, “Into Thin Air,” a personal account of a disastrous 1996 Mount Everest expedition that left eight climbers dead. That’s when Gallaher started thinking about giving mountain climbing a shot.

“I was so entranced by these mountaineers and what they were doing — minus the accident,” he said.

Gallaher joined his cousin, a mountain climber, on ascents to the Cascade’s peaks of Mount Adams, Mount St. Helens and Mount Rainier. In March 2003, The Daily News ran a photo of Gallaher and a friend at Mount Adams’ summit, where they’d planted an American flag on a 20-foot pole and four military flags to show support for U.S. troops.

At 12,276 feet high, Mount Adams was just a warm-up for Mount McKinley, which towers at 20,320 feet. Some even say Mount Everest, the world’s highest peak, is a good prep mountain for Mount McKinley, which has unique difficulties, Gallaher said. Its high latitude means the air is thinner than on mountains nearer the equator, and many climbers experience altitude sickness. Lashed by constant wind, it’s one of the coldest peaks, where the lowest temperature recorded was 95 degrees below zero (Fahrenheit), according to the National Park Service’s Web site, www.nps.gov.

On Gallaher’s trip, the temperature dropped to 40 below zero at camp overnight. Crawling out of his sleeping bag on cold mornings to answer nature’s call was one of the worst parts of the trip, he said, calling it “just misery.”

To adjust to the altitude, Gallaher’s team followed a strict climatization protocol of climbing high and sleeping low. In this way, they leapfrogged to the summit following the West Buttress route.

Instead of hiring porters or using mules to haul their gear, fuel and food, as climbers do on Mount Everest, the team used sleds roped to their packs to tow supplies up Mount McKinley’s icy, steep terrain. At 14,000 feet, they left the sleds at camp and continued up with just their packs. They climbed roped together in case someone slid into a crevasse.

At the end of each long, tough day, the team would set up camp, where they built protective snow walls around their tents to keep them from blowing away. They would build a latrine from blocks of ice and snow and squat over a “Clean Mountain Can,” which they’d have to pack out with them.

On May 25, it was time for the final leg to the summit. It proved to be the most arduous part of the journey for Gallaher. The last hour, while climbing the Pig Hill summit ridge with 1,000-foot drops on each side, he worried he wasn’t going to make it.

“It became more mental than physical,” he said.

But he pushed through. At the top, the weather was better than expected, with low wind and high visibility.

“It was a wonderful, wonderful day,” said Gallaher, who, as a military veteran, felt it was “kind of neat” to reach the summit on Memorial Day.

The round-trip hike from high camp at 17,000 feet to the summit and back took 12 hours. Eager to get home, the team made it back to base camp the next day. Then the clouds closed in, and the planes that would take them to Anchorage couldn’t land.

Gallaher missed his family. He’d talked to his wife and girls twice on the trip by satellite phone, which was well worth the $50 cost for 15 minutes, he said. Although he’d enjoyed his time on the mountain, he knew his absence was hard on his family, and the experience seemed a little self-serving, he said.

There was plenty for loved ones at home to worry about. The media had already broken the news that one man had died of a heart attack on the mountain and another was missing after leaving his team behind in his impatience to reach the summit.

Back in Kelso, Shelly Gallaher tried to stay busy.

“If I sat and dwelled on it, it does get a little nerve wracking,” she said last week. To make the time pass, she took her girls to Disneyland, she said.

After two days at base camp, the skies cleared enough for a plane to land. Gallaher was among those chosen for the first flight back. As it turned out, it was the only flight of the day. After the plane took off, the pilot said he couldn’t go back for the rest of the team because the weather was closing in again. Gallaher’s “Catholic guilt” kicked in, he said, but he was grateful to be one of the few going home.

Saturday, he returned to Kelso for a joyous reunion with his family. He’d lost 10 pounds on the trip. His quest to try high-altitude mountaineering was fulfilled, and for now, he’s satisfied.

“I don’t know if I can do that over and over again,” said Gallaher, who returns to work Wednesday managing the Longview Wal-Mart pharmacy. “I got my taste, and that was enough.”