From .com, back in 2013/14. http://www.nufc.com/html/2013-14html/2013-10-19liverpool-h.html
Crowd: 51,703 including 3,200 visiting fans, who let off two smoke bombs and one ear-shattering banger.
United's refusal to place match tickets on public sale in an attempt to plug season tickets and membership resulted in over 600 unsold seats in home areas (52,351 were present for the visit of Liverpool to SJP last season).