How many professional baseball teams have covered fields to play on?
Currently, 6 teams can have a cover while playing at home.
Tropicana Field (Tampa Bay Rays) is a domed stadium. Chase Field
(Arizona Diamondbacks), Rogers Centre (Toronto Blue Jays), Miller
Park (Milwaukee Brewers), Minute Maid Park (Houston Astros) and
Safeco Field (Seattle Mariners) all have a retractable roof. For
the 2009 season, the Minnesota Twins played in a domed stadium
(Hubert H. Humphrey Metrodome), but in the 2010 season they will be
moving to their new Target Field which is an open stadium. A new
stadium with a retractable roof, Marlins Ballpark, is under
construction for the now Florida Marlins, due for a 2012
completion.