The former third baseman and radio broadcaster died from complications of bladder cancer last week in Arizona.
The funeral for Ron Santo will take place Friday and will be streamed live here on ABC7Chicago.com.
Many family members and former teammates flew in for the service.
"We're doing alright, hanging in there ... I was fortunate to spend the last day with my father before he passed on," son Jeff Santo said Thursday.
Santo's casket, adorned with his retired number 10 flag, was carried into the church Thursday afternoon.
"He just had that character. He had that courage, that fight. And I just think he was one of those special people that appreciated what he had," his son told ABC 7.
Inside the Catholic church, a framed jersey and gold glove accompanied Santo's casket as family and friends bid a private farewell.
"It's very somber but on the other hand, there's a lot to celebrate. It's a very great life," said John McDonough, former Cubs president.
"That guy was just an amazing human being, with all the ails he had. And nobody really knew how bad it was," said former Cubs pitcher Milt Pappas. "The diabetes got worse and losing his legs and open-heart surgery. You know, whatever could go wrong went wrong. And yet he always had a smile on his face."
"He brought a lot of joy to a lot of people. But I'm glad that I can be here when so many from our city and among his fans, along with his family, pray for him," Cardinal Francis George told reporters.
The gathering included Cubs General Manager Jim Hendry, broadcasters Len Kasper and Bob Brenly and former Cubs pitcher Kerry Wood, as well as Santo's former teammates from the bittersweet 1969 season.
"I'm remembering the good times with me and Ron. And love it. Ronnie, I miss ya," said Glenn Beckert, former Cubs second baseman.
As a young man, Santo struggled quietly with diabetes before using his celebrity to draw attention to the disease. He was a Cub with a lion's heart who lost his legs but not his spirit.
"Just imagine how we would have felt to watch him to walk up on a podium in Cooperstown with two artificial legs," said Wayne Messmer, Cubs public address announcer.
The public visitation line wrapped around the block with thousands of people -- including Sox fans -- braving the cold for hours, all for a chance to offer tears and thanks.
"He was a good man. And I owe it to him because I watched him all these years," said Dan Morrison, Sox fan.
John Anast was first in line, arriving at 6 a.m.
"I cleared my schedule to come on down here, and I figured my little personal thing was that I wanted to be here 10 hours early for number 10," said John Anast, Cubs fan.
"I think a little bit of Cubdom died with him. Really, he embodied the Cubs," said Stephanie Romeo, Cubs fan.
Despite the Windy City's cold temperatures, Santo said he felt nothing but warmth from Chicagoans who loved his father.
"He would be amazed by it all. He was such a humble man and giving person that he would really be amazed by it all," said Jeff Santo.
Thursday's public visitation began at 4 p.m. and scheduled to end at 12 a.m. at Holy Name. Fans were told to be in line by 11 p.m. to ensure entry into the church. Seating was limited.
Santo's funeral is set for 10 a.m. Friday at Holy Name. Eulogies will be delivered by Cubs Chairman Tom Ricketts, baseball Commissioner Bud Selig and Pat Hughes, Santo's partner on WGN radio.
After the funeral service Friday, a procession will leave Holy Name, pass by the WGN radio studio at the Tribune tower on Michigan Avenue and head north to Wrigley Field.
Fans are invited to gather outside the stadium at 12 p.m. Friday to view the procession.