Marine One, the president's helicopter, flew over the debris, and he met with families of the victims.
"The families that I met with showed incredible strength and grace through unimaginable pain and difficulty," he said later, speaking at a firehouse.
"The whole country's thinking about you, and we're going to make sure that we're there every step of the way as we go through the grieving, the mourning, the recovery," he said. "We're going to be strong right alongside you."
At least 41 people were killed. Two are still missing.A month after the landslide, the mud remains so deep and wet in places that searchers struggle to get through it.
Ben Woodward, a firefighter from eastern Washington, is one of the reinforcements brought in to take over the difficult search for bodies from local residents.
"Our motivation is finding closure for the families," Woodward said. "We're looking for their loved ones, that's our motivation for everybody out here, and we take that in daily."
The death toll is lower than first feared but the loss remains enormous in this small community.
Volunteer firefighters Jan and Jeff McLelland were among the first rescuers to reach those trapped in the landslide.
"I've cried a lot," Jeff McLelland said. "I've gone through various emotions. I've been, you know, um, from that first day when I walked out there and looked at it, I cried."
"When something makes you sad, you feel so sad," Jan McLelland said. "There's a bit more of an extreme to your life that you didn't feel before."
In Darrington, the flags have been flying at half staff for a month.
"Being able to overcome that tragedy is going to be a long and hard process," Mayor Dan Rankin said.
Asked if the area could ever recover, he said, "Will we ever be whole and well? No."
Part of making this region whole is re-opening the only highway through the valley. But a stretch of the road, more than a mile long, remains under the mud with no estimate for when it will be re-opened.