Roof collapse. Block party. Riots. What started as informal student gatherings tied to St. Patrick’s Day has morphed into one of San Luis Obispo’s most coordinated annual public safety efforts.

The event grew from house parties into large, unsanctioned neighborhood celebrations near Cal Poly. Injuries, resident advocacy, policy changes and increasing institutional involvement have changed how the city and university handle the weekend.

But the event didn’t randomly show up one March. Community members frequently compare St. Fratty’s Day to earlier student traditions that ended after escalating disorder.

1990

POLY ROYAL ENDED BY RIOTS

Poly Royal began in the 1930s as Cal Poly’s annual open house, featuring agricultural exhibits, parades and rodeos. By 1990, the event drew more than 100,000 visitors to a city of roughly 41,000 residents.

On the night of April 27, 1990, crowds spilled into off-campus neighborhoods after a bicyclist collided with a vehicle, prompting police response. The situation escalated as people threw rocks and bottles at officers, who deployed tear gas and high-pressure water hoses to disperse the gathering.

Police arrested thirty people that night. The following evening, another crowd of about 2,000 people gathered, breaking car windows, lighting bonfires and throwing debris at police.

By the end of the weekend, 80 people were arrested and about 100 were treated at local hospitals. Multiple officers were injured, including some who suffered broken arms and wrists. In response, Cal Poly President Warren Baker announced Poly Royal would be canceled indefinitely. While portions of the tradition later returned in smaller forms such as Open House, the original large-scale festival never resumed.

2004

MARDI GRAS RIOT

By the early 2000s, Mardi Gras in San Luis Obispo had grown into what Mustang News later reported as “the biggest celebration west of the Mississippi,” drawing thousands of students and visitors.

That ended on Feb. 21, 2004, when an estimated 5,000 people crowded streets near campus. Revelers threw rocks, bottles and firecrackers at officers, prompting police to deploy tear gas, pepper spray, non-lethal bullets and beanbags. 180 people were arrested that night, multiple officers were injured and the city later reported spending roughly $100,000 on enforcement.

2005

MARDI GRAS CELEBRATIONS OVER

San Luis Obispo launched a major enforcement campaign for Mardi Gras in 2005, bringing in hundreds of officers in riot gear, tripling fines for public drunkenness, noise and public urination and promoting messaging that “the party is over.” Arrests dropped to about 82, a 58% decrease from 2004.

By the late 2000s, Mustang News reported Mardi Gras had largely disappeared as a party weekend. Residents would later reference both Poly Royal and Mardi Gras when urging action on St. Fratty’s Day.

2010s

ST. FRATTY’S DAY EMERGES

Unlike Poly Royal or Mardi Gras, St. Fratty’s Day developed informally through student networks and social media, expanding from house parties into neighborhood-wide celebrations near campus without official organizers.

March 7, 2015

Credit: File | Mustang News

THE ROOF COLLAPSE

At 6:21 a.m. on March 7, 2015, a garage roof collapsed during a St. Fratty’s Day party on Hathaway Avenue. Nine people were injured. Two required assisted rescue and one suffered severe but non-life-threatening injuries. Police estimated nearly 1,000 people were nearby, and the building was declared a total loss.

Two weeks later, Cal Poly Greek leadership submitted a letter apologizing and calling the collapse a “wake-up call,” and noted the party was not officially registered.

Feb. 6, 2025

COMMUNITY REFLECTION

In the years following the collapse, San Luis Obispo introduced voluntary party registration and Safety Enhancement Zones with doubled fines.

Feb. 21, 2023

RESIDENTS DEMAND PREVENTION

Residents packed City Council in February 2023 calling for St. Fratty’s Day to be canceled and for expanded enforcement windows.

March 2024

Resident’s in Muir Hall walked over broken ceiling tiles that stretched the length of the hallway on March 16, 2024. Samantha Elliot | Courtesy

DAMAGE MOUNTS AND ENFORCEMENT INTENSIFIES

Ahead of St. Fratty’s Day in 2024, San Luis

Obispo police prepared expanded Safety

Enhancement Zones across the first three weekends of March, with doubled fines and increased staffing. Police also deployed surveillance tools including neighborhood cameras and drones, and discussed the use of undercover officers.

Despite these measures, the 2024 St. Fratty’s block party resulted in more than $24,000 in damages at the Red Bricks residence halls and a record high of 150 reported criminal offenses, including unruly gatherings, public urination, noise violations and public alcohol consumption.

Cal Poly President Jeffrey Armstrong condemned the damage in a campus email following the weekend.

March 2025

Credit: Jai Gulati / Mustang News

THE FIRST ‘MORNING ON THE GREEN’ — A MUSTANG MUSIC FESTIVAL

On March 10, 2025, Armstrong urged responsible celebration and promoted Morning on the Green as an alternative to off-campus block parties. Students arrived at the festival by 3:15 a.m., lines surged by 5:20 a.m., barricades collapsed around 6:15 a.m. and hundreds attempted block parties near Hathway Avenue by 7:45 a.m. Four arrests were reported.

San Luis Obispo reported spending roughly $115,000 on containment. Cal Poly disclosed spending $1,167,157 on the weekend.

2026

THE PLANS FOR ST. PATRICK’S DAY 2026

Cal Poly announced the festival capacity doubled to 10,000 for this year, along with Odd Mob and Walker & Royce headlining. Later, to deal with the demand, four thousand additional tickets were released during the Feb. 19-20 window. Finally, the city announced a zero-tolerance enforcement plan with Safety Enhancement Zones across all March weekends.

St. Fratty’s Day has transformed from casual, student-run student parties that it once was into something more coordinated, involving campus festivals, Safety Enhancement Zones, multi-agency policing and seven-figure spending. Poly Royal and Mardi Gras are examples of how the earlier traditions ended in the wake of unrest. St. Fratty’s Day, instead, has been reformed with containment, programming and enforcement.

This story originally appeared in the March printed edition of Mustang News. Check out more stories from the issue here.