As his body lay in repose inside the museum, mourners, friends and baseball fans came by the carloads to pay their last respects to O'Neil, a man who had become the face and voice of "black baseball" and who'd died of congestive heart failure a week earlier.
"It's been a steady stream of folks all day long," said Bob Kendrick, marketing director for the museum. "But it doesn't surprise me; it really doesn't."
Kendrick said people started lining up for the memorial around 7 a.m. CT, which was an hour before the museum was scheduled to open.
"We were able to get things situated a little bit earlier," he said. "We got them off the street and out of the cold. So we just opened the line a little earlier, and it's been a steady stream."
The stream brought the famous and the not-so famous inside the museum, where O'Neil's body lay on the Coors Field of Legends. Ernie Banks, Billy Williams, Ozzie Smith, John Mayberry and Pete LaCock were among some of the Major Leaguers who came to the museum to view O'Neil, who will be laid to rest here on Saturday morning in a private service.
"You've got everything from the hip-hop generation to just older people in the community and people who were just out of the community, and older people who were out of the community," said Phil S. Dixon, a Negro Leagues historian. "Blacks, whites, it was just a real diversified group.
"I think that's a testament to what he did."
Dixon said he didn't believe any other Kansas Citian could have brought such a wide range of whites, blacks and Latinos together. The city, of course, has had its rich and famous, but no person, he said, spoke to the whole of the city and elsewhere the way O'Neil did.
"He's a big figure all over -- everywhere," said Jesse Rogers, who played for O'Neil when he managed the Kansas City Monarchs. "He was a good man that enjoyed life -- that did anything for anybody that he could.
"He was just a gentle man -- that's all I can say."
Others talked about what O'Neil means to Kansas City, if not to every place where men of great character leave their stamp on society.
"I think all of this community thinks Buck was their Lord and savior almost," said Dewey Alexander, a batboy for the Monarchs during O'Neil's playing days. "He did so much for this community. I think he brought this community together."
Listen to other men and women here, and O'Neil was that and more. To people at the museum, he was their signature. Kendrick called the place the "House that Buck Built," and it would be hard to argue that he wasn't, said Don Motley, the museum's executive director.
"That's why we had to have it here," said Motley of holding O'Neil's repose here. "Was there any other place better?"
No, said Kendrick. Nor could the museum not open its doors to the masses. It wanted everybody whom O'Neil touched to come and celebrate his life and not necessarily to mourn his death.
He was a man, Dixon said, who kept the story of black baseball alive.
"For many people, Buck was the connection," Dixon said. "He put a face on the history. That was real important, because anyone can talk about it. But he was like a living part of that history, and you can see the difference. He made a difference."
By all accounts, Dixon is right. His assessment of O'Neil mirrored the sentiments of others here and elsewhere.
Inside the museum, one of the well-wishers posted a ceramic placard that summed up O'Neil's legacy. It read: "It's a rare person who can take care of hearts while also taking care of business."