Mayor Lewis said the devastation was so catastrophic that city officials rushed to print new street signs to help guide rescuers and residents through the newly mangled and unfamiliar landscape.
President Obama will travel to the area Sunday to witness the damage.
He spoke about the people of Oklahoma, briefly, during a presentation at the White House on Wednesday.
"While the road ahead will be long, their country will be with them every single step of the way. That's who we are, and that's how we treat our family and friends and our neighbors wherever they are in the country," he said.
"We're going to help them recover."
Insurance claims related to Monday's tornado and storm in metropolitan Oklahoma City are likely to top $2 billion, said Kelly Collins, a representative of the Oklahoma Insurance Department.
Craig Fugate, the Federal Emergency Management Agency administrator, told CNN the agency is in "good shape" to support the recovery in Oklahoma and in other disaster zones, such as rebuilding after Hurricane Sandy in New Jersey and New York.
"We got full allocation last year with the Sandy supplemental funds. We are looking to continue the response here as well as the previous disasters."
But "if we have another hurricane, we may need more money," he said Wednesday.
For her part, Secretary of Homeland Security Janet Napolitano traveled to Moore to thank first responders and show her support.
"Our commitment is to be here for the duration -- to work with our federal, state, tribal, local and community partners in the coming days, weeks and months to help you recover and rebuild from this terrible tragedy and emerge even stronger," she said.
Those helping in Moore include police and firefighters from Joplin, Missouri -- a city all too familiar with grief and devastation.
Wednesday marks the second anniversary of a tornado that pulverized Joplin, killing at least 158 people. It was the deadliest single U.S. tornado since federal record-keeping began in 1950.
"We remember the amount of assistance that we received following the tornado two years ago, and we want to help others as they helped us," said Joplin City Manager Mark Rohr.
"We know too well what their community is facing, and we feel an obligation to serve them as they have served us."
'We just didn't get there fast enough'
Help came from seemingly everywhere the day the tornado struck.
Dustin Ellison ran to the rubble of a convenience store to help get at people trapped in a freezer, which had collapsed.
"It was one big pile of rubble. We knew people had went in the freezer, and we knew that there was no way they had come out," he told CNN's Tapper.
"We just didn't get there fast enough."
One of the victims Ellison and the others found there was 29-year-old Megan Futrell. Another was her infant son, Case.
"She was protecting him," he said.
"Your instinct, when you see that is, for me, I ran towards it. There's probably a lot of people that didn't, or that wouldn't, but not around here."