President Obama tours tornado-stricken Joplin, Mo.

After walking through chillingly empty vistas of twisted rubble and shards of homes, President Obama drew wild cheers from this conservative town when he pledged to help rebuild from last week’s crippling tornado.

“You look out at the landscape there, and there have to be moments where you just say, ‘Where to begin? How to start?’ There are going to be moments when, after the shock has worn off, you feel alone,” he said at a community memorial service attended by more than 2,000 people.

“I can promise you that your country will be there with you every single step of the way. We’re not going anywhere,” Obama said, his voice booming over shouts and whistles at Missouri Southern State University.

The president got a bird’s-eye view of the devastation as Air Force One flew over the town of 50,000 people en route to the small local airport. From the air, it looked as if a gigantic bulldozer had cleared a six-mile path straight through the center of town.

At least 139 people were killed and more than 900 injured in the twister, which was an EF-5, the highest rating on the Enhanced Fujita Scale, with winds of at least 200 mph. Officials said Sunday that 43 people remained missing, but families of four of those had reported them dead.

Before the memorial, Obama toured areas of the worst destruction, where big-box warehouse stores were leveled and entire neighborhoods converted into piles of broken two-by-fours, crumbled concrete and smashed, twisted cars.

Thousands of survivors lined Joplin’s main thoroughfares.

“This town is beat, but we’re not broke,” said Catherine Maples, who wore a T-shirt scrawled with the words, “A country town can survive.”

A few times, Obama stopped to share handshakes, hugs and words of encouragement.

“Sorry for your loss,” he said, embracing one distraught woman.

Hugh Hills, 85, the owner of a lawn care business, was surrounded by his family and holding an American flag. He told the president and his entourage about seeing news of the coming tornado just as he was pulling a pot pie out of the oven.

Hills wrapped himself in a quilt and ducked into a closet, he said, as the second floor and half of the first floor of his house collapsed around him.

“These are just things,” one of his family members said, pointing to the debris and the house. “We’re just glad Grandpa made it.”

In the midst of the deadliest tornado season since at least 1953, Sunday’s visit paralleled a trip Obama made last month to Tuscaloosa, Ala., scene of another devastating twister. Several residents of that city have come to Joplin to provide advice and moral support.

“When we were in Tuscaloosa a few weeks ago, I talked about how I had not seen devastation like that in my lifetime,” Obama said at the memorial. “You come here to Joplin and it is just as heartbreaking, and in some ways even more devastating.”

But as he recounted many examples of Joplin residents who sacrificed their lives to save others or carried wounded citizens on mattresses in the backs of their pickups, he said there was much to learn.

“How we respond when the storm strikes is up to us. How we live in the aftermath of tragedy and heartache, that’s within our control. And it’s in these moments, through our actions, that we often see the glimpse of what makes life worth living in the first place,” the president said.

The heroes around us, he said, are “driven by love.”

Missouri’s Democratic governor, Jay Nixon, reminded those at the memorial of the state’s reputation for obstinacy and resiliency.

“For us, the living, there is work to do. God says, ‘Show me. Show me,’ ” Nixon said, drawing laughter as he referred to the state’s famous motto.

Later Sunday, as the one-week anniversary of the brief but vicious storm arrived at 5:41 p.m., officials declared a moment of silence from a site near the city’s ravaged hospital, St. John’s Regional Medical Center. Hundreds gathered in the broken landscape.

Local radio station KZRG, whose nonstop disaster coverage has been a lifeline since the storm, debuted a song composed for the tragedy. “Sing Again” blasted from loudspeakers and car stereos across town.

Earlier, some who watched Obama pass by appeared dubious. “People for the most part are saying, ‘Stay home and send money,’ ” said Kristi Santee, a Joplin resident.

“I don’t know how many tax dollars it took for him to come down and tour what we already know,” Maples said.

But many at the community memorial were moved to applause and tears.

“Well, I didn’t vote for him. But I’m glad that he was here,” said Rick Morgan, an unemployed computer programmer who crawled out of the rubble of a Dillons grocery store after huddling with about 40 people in a 6-by-10 produce cooler.

Throughout Obama’s speech, Morgan seemed overcome with emotion.

“I can tell you, the people in that cooler were doing one of two things: screaming hysterically or praying. I don’t think our prayers were any better than the people who were killed, but I think God had mercy on us and spared us,” he said.

“I’ve heard stories and stories like that — little bubbles of grace. Homes totally destroyed, except for a little closet where a husband and wife and five kids were standing. It could have been so much worse.”

kim.murphy@latimes.com