This started as a reply to a reddit poster claiming a USA-Turkey match in 2010 was “the highest attended soccer match ever”
According to this the attendance was 55,407. Nice, but not the highest ever for soccer.
http://www.ussoccer.com/news/mens-national-team/2010/05/turkey-game-report.aspx
But not the larget for soccer that I can find. Portugal played the USA at RFK during the 1996 olympics, attendance was 58,012.
http://www.dcconvention.com/Venues/RFKStadium/UniqueSpaces.aspx
Also MLS Cup 1997 at RFK featuring home side D.C. United was attended by 57,431 people.
http://en.wikipedia.org/wiki/MLS_Cup_’97
Also, the LA Coliseum would sell out for soccer matches, albeit ones not featuring the USA. Capacity is 92k
http://articles.latimes.com/1999/apr/29/news/mn-32450
Turns out the USSF has a page with attendance records, and the USA-Turkey game, or the others mentioned by me above, would not make it, as the minimum cutoff is around 78,000. Maybe the US turkey game was the best attended USMNT during the previous world cup cycle?
http://www.ussoccer.com/teams/us-men/records/attendance-records/largest-crowds-in-us.aspx