MILWAUKEE—Baseball’s yearly general managers’ meetings and quarterly ownership meetings, held jointly this week here at the Pfister Hotel, ended Thursday with a sequence of activity that ensured significant changes to the sport moving forward.

The Houston Astros will move from the National League Central to the American League West, commissioner Bud Selig announced. The realignment will most likely occur before the 2013 season, he said.

Meanwhile, the ownership of the Astros, after a unanimous vote of approval Thursday by team owners, was officially transferred from Drayton McLane, who owned the team for 19 years, to a group headed by Jim Crane.

Selig also said Thursday that the number of wild-card teams in each league would be increased to two. That change, Selig said, could occur as soon as 2012.

“This was, in my opinion, what I think will prove to be a very historic day in this sport,” Selig said.

Baseball’s last realignment occurred before the start of the 1998 season, when the Milwaukee Brewers moved from the American League to the National League. The latest realignment would place 15 teams in each league and five in each division, ensuring that interleague games would take place every day of the season.

The addition of a second wild-card team in each league, meanwhile, will require a play-in game or another series before the start of what is called the division series.

“The greatest thing this sport has going for it is its history and its tradition, and the more you’re around the more you understand that,” Selig said. “You try to disturb that as little as you can. But I think this is great for the long term.”

The sale of the Astros, for over $600 million, was first announced in May and finally approved after a long investigation of Crane and his large group of investors by baseball’s ownership committee and executive council.

“It was a long vetting process,” Selig said of Crane. “Sometimes in life you have to go through all that. We did. We spent an enormous amount of time. I’m very comfortable today telling you he has put together a really blue-ribbon group.”

These announcements were made against the backdrop of continuing talks between baseball and the players association for a new collective bargaining agreement. The realignment and scheduling changes were characterized Thursday as a collaborative effort.

Rob Manfred, baseball’s executive vice president for labor relations and human resources, said he was “really confident” the deal would be completed in the near future.

“I think we will finish an agreement,” Manfred said. “It’s a process. It’s hard to pick exactly when anything is going to happen. But I think that we’ve made good progress, and I’m hopeful we’ll push it through.”