Purchases were limited to one per person, so coin dealers had to use proxies.
First in line was a vet in a wheelchair, Joe Grover of Kensington, who opened the box to show off the shiny coin for the media.
Outside, private security guards for one group were collecting the bagged coin boxes in a bigger box, before escorting the purchasers to a nearby hotel to get paid.
One overzealous fellow quizzing a reporter said, "Everyone's armed here, so keep that in mind."
Grover was also first in the morning line, where the wait was for 500 golden tickets conferring the right to return for the noontime sale. Mint officials started handing them out about 8:15 a.m., eventually turning about 200 people away.
But that was hardly the beginning.
Grover said he arrived at 2:30 p.m. Monday, after a friend called about an easy way to make some cash.
Sharon Patriaco, of Lakewood, N.J., also arrived Monday afternoon, and said the crowd grew to "hundreds" by 11 p.m.
"Four hundred dollars" seemed to be the going rate for waiting in line, judging from a quick survey this morning of a dozen people with $300 to $600 mentioned as the range.
Spokesman Tim Grant said the scene this morning was like nothing he'd seen in his 30 years with the Mint.
The 500 limit was just for today, Grant explained, since the coins can be ordered online or by mail from the Mint.
First-day editions, however, are especially valuable, and the key is obtaining a dated receipt, so an authenticator can create a specially marked case.
Then there's the Kennedy mystique, coupled with reverence in the coin world for the design of the Kennedy half-dollar, making this 50th-anniversary edition even more valuable to collectors.
The commemorative coins are also available in much-cheaper silver sets.