Ronnie and Donnie Galyon, of Beavercreek, Ohio, were born joined at the abdomen.
Tips about potential acts of mass killings have spiked, and law enforcement appears to be paying close attention to threats.
Performers at Gem City Shine included Chance the Rapper and Stevie Wonder.
The Ohio city's mayor, Nan Whaley, tweeted that she is "so excited" about the Sunday event.
Adam Bowles hopes to raise at least one dollar for each of the 2,300 miles driven — funds that will go toward supporting the victims of the El Paso massacre.
Whaley said she was just doing her job when the president insulted her.
The Dayton Police chief said that the gunman who carried out a deadly mass shooting in Dayton planned the attack in advance.
"We’ve heard politicians send their thoughts and prayers while failing to act," the 10-time Grammy winner said. "We are done with that."
Native Ohioan John Legend went to Dayton to speak out for gun control following the deadly shooting that killed nine people.
“This is a moment to reflect ... and to remember the individuals whose lives were cut short," said executive editor Martin Baron.