When the Boulder International Film Festival debuted in 2005 with 35 films and a little more than 4,000 guests, the city of Boulder was plenty big enough to host it. The challenge wasn’t the space so much as whether BIFF would last long enough to become a tradition. It did, and for its 21st year, the festival expects to welcome 25,000 film enthusiasts, media, industry members and movie stars (Shirley MacLaine, Alec Baldwin, and James Franco are just a few of the actors who have attended in the past) during its March 13-15, 2025, run. But the city — a college town and bedroom community of 100,000 year-round residents — hasn’t really kept pace when it comes to venues, said Kathy Beeck, who co-founded the fest with sister Robin Beeck.