Once home to fraternal secret society meetings and civic agencies, the Napa River Inn's Hatt Hall was named after Captain Albert Hatt, who founded the Napa Mill in 1884. Then known as "The Hatt Building", many locals still affectionately refer to it as such. Hatt Hall offers a unique artisan feel to your next meeting or event. The only originally existing meeting room of its kind in Napa Valley, the Hatt Hall was originally a music salon established in 1884. Mrs. Alma Hatt, wife of the original proprietor Captain Albert Hatt, held concerts while Napa's Secret Society held monthly meetings which are a mystery to this day. Just outside the Hatt Hall meeting room are 7 well-appointed Historic Deluxe Suites.

The entire second floor of this building was once a roller rink. The original wood floor installed in the 1800's still exists after meticulous renovations. Many locals remember coming to the Hatt Building to roller skate and later, to purchase feed for their live stock when the Napa Mill was a feed and grain store.

Today, the Napa River Inn continues to host community events in support of the local arts community, civic leaders, and local non-profit organizations. The Hatt Hall has 1925 square feet of unobstructed space with 14 foot ceilings. Large scale windows original to the Mill provide natural daylight. Hatt Hall is equipped with complimentary wireless access, a built in screen which drops from the ceiling, ambient lighting, DVD stereo system, podium, and microphone. Although perfect for groups of from 10-96, the maximum allowed is 100.