Michael Bradley is now the second American player to appear for Borussia Moenchengladbach, following Kasey Keller's run with the club from 2005-07. The club moved to Burussia Park to start the 2004-05 season.
The stadium has a listed capacity of 54,067, but that includes standing areas. Though standing areas aren't allowed at the higher levels of the English and Scottish leagues, the Bundesliga does allow them. However, UEFA and FIFA don't, and most recent Bundesliga stadiums are designed to switch between standing and seating sections. Borussia Park's 16,145 capacity for standing converts to 7,718 seats.
From 1919 until the end of the 2003-04 season, the club used the Bökelbergstadion. With a listed capacity of 34,500, the stadium was considered too small to host international games. Oddly enough, the new Borussia Park got the unenviable distinction of being the largest and newest stadium in Germany not to be used for the 2006 World Cup.
Borussia Moenchengladbach returned to the Bundesliga for the 2008-09 season, but they don't normally sellout the Borussia Park. The supporter groups use the North Stand, designated as "the singing area." It's club practice not to allow visiting fans into that part of the stadium. The club goes so far as to warn ticket holders not to give North Stand tickets to away support.
The club is also well aware of the potential for problems with standing areas. Though the Borussia Park still uses pens to fence in the standing areas and relies on self-policing as much as stewards, it's in cooperation with the supporter groups. As the club puts it on their official English site: "Freedom for the North Stand" does not mean "anarchy in the block!"
One last thing, "Borussia" is another way to reference Prussia, the area of Germany where Moenchengladbach is located.