Among them were about 140 officers from the Hagerstown Police Department, Washington County Sheriff's Department and Maryland State Police, Sgt. Steve Bussard said.
The Alsatia Club had received a potential threat of violence directed toward black participants of the Mummers' Parade earlier in the week, but it was considered "unsubstantiated and not corroborated," Hagerstown Police Department Lt. Mike King has said.
A Maryland State Police helicopter flew overhead at times as a precautionary measure, he said.
A vendor who was selling fake guns along the parade route was "ordered to discontinue the sales," early on in the parade, Bussard said.
Despite the extra police presence, the parade went on.
Before the parade started, several participants were busy preparing their floats for showtime.
Dressed in a Cruella De Vil costume, Leigh Fox decorated the Beverly Healthcare of Hagerstown float with cobwebs.
Fox, who is Beverly Healthcare's director of admissions and marketing, said she likes when paradegoers recognize the nursing home residents.
She said one of the residents, Nancy Rockwell, was in the parade when she was a little girl and would be on the float Saturday.
Louise Noel was to take a birthday ride in the Washington County Free Library Bookmobile.
"She's 100 years old and we're celebrating our 100th year," said Chris Henry, a substitute bookmobile driver, before the parade.
"I think she's just gonna wave," she said.
Members of Clear Spring Girl Scout Troops 220 and 263 were gearing up to wave and blow bubbles at paradegoers.
The 27 girls had spent the past two months making a papier-mch Earth for their float. Shianna Reed, leader of Troop 220, said the giant blue and green painted globe had fallen off the back of her truck on her way to line up for the parade, but it didn't break. The globe was circled with the gold words, "Building a better future."
"I'm excited. People are gonna see what we did," said Lindsay McCoy, 9, a junior Girl Scout with Troop 263.
Among the others excited for the parade were members of Tuckers N' Tumblers Gymnastics, who couldn't sit still before the parade started.
The TNT gymnasts practiced flips off a springboard on the float.
Rachel Taulton, 12, of Rohrersville, who won a state competition for her level, said she wasn't worried that she wouldn't land her jumps when the float started moving.
"You have to make your runs shorter," said Rachel, whose favorite flip is a round-off back handspring with a half-twist.
William Nicholas, 50, who lives in the 1000 block of Potomac Avenue, set up his front lawn with a bonfire and snacks Saturday as parade participants got their floats ready.
Nicholas said it didn't matter that the parade wouldn't pass by his house.
"There's so many interesting people who walk by that we'd like to look at," he said.