The Town of Johnstown was established in 1902, but it wasn't until 1912 that the idea of a local celebration was born with Dairy Day. The purpose of Dairy Day was to promote the dairy industry in the area, and it quickly became popular among farmers from all over the state and surrounding states. Circus-type tents were set up to house events and cattle judging, and families were invited to enjoy carnival rides, games, entertainment, and food. Dairy Day was the beginning of the dairy business in northern Colorado, but it was interrupted by the Great Depression and World War II. It was revived for several years in the 1940s and early 1950s, but 1951 saw the last Dairy Day.
In 1963, area businessmen came up with Crazy Day to attract more people to shop in Johnstown. The day proved to be very popular, and by 1968 it had evolved into an event where everyone was encouraged to wear outlandish costumes, and a parade featuring floats was added. That year, a roasted pig was served free to customers at Hays Market, which marked the start of Barbecue Day.
In 1969, Barbecue Day became the official name of the celebration, and it was moved to Parish Park. It became a 30-plus year tradition until the late 1980s, when the Chamber of Commerce changed the name to Barbecue Days and experimented with a whole weekend festival.
The last Barbecue Day was in 1999, and in June of 2000, the name was changed to BBQ Daze by the Johnstown/Milliken Chamber of Commerce. In 2006, a group of local citizens took over the organizing duties and reverted the name back to Barbecue, or more generally BBQ, Day.
Due to the COVID-19 pandemic, BBQ Day was canceled in 2020. However, in 2021 an updated parade route and increased vendor placement outside of Parish Park allowed for greater spacing and separation. The community turned out in record numbers to celebrate the theme of "Together Again" and the event continues to grow in exposure and popularity as it continues to be a premier summer kick-off event in Northern Colorado.