Clinton shook hands, cooed over small children, thanked those who urged her to run for president and even accepted a resume from a Georgetown University student at the back of the Pentagon City Costco.
In each copy of her memoir, Hard Choices, she wrote simply: "Hillary."
When civil rights titan Rep. John Lewis, D-Georgia, came through the line unannounced, Clinton threw up her hands in delighted surprise. The two spoke quietly for several moments, hands clasped, and when reporters asked Lewis if Clinton should run, he said, emphatically, "Yes."
Costco co-founder Jim Sinegal stopped by to get a book signed, and Supreme Court Justice Sonia Sotomayor just happened to be shopping at Costco and came to say hello (she skipped the line). When Sotomayor told Clinton she would read the book, Clinton replied: "You better! I read yours!"
Fatema Dariani, of Rockville, Md., arrived at 7 p.m. Friday and was the first in line. She said she became a Costco member after an employee told everyone in line they had to hold a membership to the wholesaler to get an autograph.
"It was totally worth it," she said.
Jackie Harris and her daughter, Ashleigh Hughes, of Waldorf, Md., were second and third in line and also joined Costco for the occasion.
Hughes, 22, said she's been a Hillary Clinton supporter since Bill Clinton was president.
"She's gone down the checklist," Hughes said, ticking off Clinton's resume as first lady, senator and secretary of state. "She's respected by so many."
Frank Colasonti Jr., sixth, in line, said he drove most of the day Friday from Birmingham, Mich., and spent the night waiting outside the Costco. Colasonti said he decided to make the 24-hour round-trip after he learned Clinton wouldn't be doing an event nearby.
"She's been a -- just been in our hearts from the beginning," Colasonti said, growing emotional.
Asked about Clinton's recent defensiveness over her past opposition to gay marriage, Colasonti said he and his husband, the first couple married in their county when a federal judge struck down Michigan's gay marriage ban last year, weren't bothered.
"As long as we're moving forward, it's fine," he said.
In the parking lot outside, the bus from the super PAC Ready For Hillary stood parked next to where the line snaked around, doubling back on itself several times. Volunteers handed out snacks and Capri Suns, signs and posters featuring the now-famous shot of Clinton typing on her Blackberry, captioned with "#Ready."
The bus will follow Clinton on her book tour and visit conventions, festivals and other events throughout the fall, drumming up support for a Clinton campaign and backing the 2014 candidates Clinton endorses. Aboard the bus, Ready For Hillary's communications director, Seth Bringman, said the book tour had given him an up-close look at the mounting excitement around a Clinton candidacy.
Bringman said their stock of posters disappeared "in like two seconds" at an event at George Washington University Friday night, and that young people had been donating in small amounts, particularly $20.16, in droves. He said the group has already registered more than 2 million supporters, a list of whom an eventual Clinton campaign could buy or rent for its own organizing efforts.
"It's been one of the most inspiring things about the whole [bus tour] campaign," he said. "Enthusiasm has only grown."
A small group of Republican National Committee staffers stood at the Costco entrance, handing out flyers that challenged Clinton's record as secretary of state. Passersby posed for pictures with someone wearing a squirrel suit and a t-shirt that said "another Clinton in the White House is nuts."
"I think [Democrats are] worried about her tenure at State," said Raffi Williams, an RNC spokesman. "She can't name her signature accomplishment."
"She got $50 million of free media last week," Williams said. "We're making sure we hold her feet to the fire."
But Bringman said Republicans are reaching for something, anything, they could make stick to drag Clinton down.
"It just shows how great of a candidate she would be," he said. "Supporters say [those comments] make them more determined than ever."
justice sonia sotomayor going to costco to meet and buy hillary clinton's book is what gives me strength. pic.twitter.com/5SFiMKNcoc— Brooks W. Boron (@brooksboron) June 14, 2014