The Maryland Jockey Club estimates that the infield party first became popular when Secretariat won the Preakness in 1973, as the general manager at the time used the big name to attract crowds. What resulted was a fairly calm time for the infield with picnic blankets, face painting, and some grills and coolers here and there.
Things started to get more extreme around this time, as there didn't seem to be many rules about how much outside alcohol you could carry in. People used everything from wagons to couches to carry in their party supplies.
During this era, binge drinking, getting injured, being escorted out, and passing out on site were all common occurrences. It all came to a head in 2007 when a video of young men participating in the “running of the urinals" went viral, causing concerns for the health and safety of infield fans.
The Maryland Jockey Club banned outside alcohol altogether, and the crowds reflected the change (77,850 compared to 112,222 the year before). The ban contributed to a loss of more than $25 million in revenue between 2007 and 2009.
MJC launched a campaign to reinvigorate the infield, featuring Kegasus (a binge-drinking centaur) and attracting big-name acts like Maroon 5, Bruno Mars, and Zac Brown Band. They have also started the Mug Club, where fans can buy one refillable mug for the whole day. This year, on May 17, musical performers include Lorde and Eli Young Band.