On June 1, 1905, the Lewis and Clark Exposition opened to the public. Roughly 40,000 visitors arrived at the fair by ten o'clock in the morning. No other exposition was honored with more distinguished guests than the opening day of the Portland Exposition, which included Vice President Charles W. Fairbanks, Speaker of the House Joseph Cannon, five state governors and a large congressional delegation.

When the idea for a Portland fair surfaced in 1894, it was intended as a local industrial exposition. Organizers expected that it would attract little outside interest due to the large distance from major centers of population and because so little time had passed since the 1904 St. Louis Exposition. Many states had already spent money on the St. Louis Exposition and lacked the funds to support the Lewis and Clark Exposition. Shortly following the groundbreaking ceremony on April 7, 1904, President Theodore Roosevelt appropriated $475,000 for the government exhibit. This was a financial turning point for the exposition and helped create support from other states. Soon, the Lewis and Clark Exposition began to outgrow previously held plans, expectations, and hopes.

The fair was designed to showcase to the world the economic potential of the region, and provide a jumpstart to the burgeoning economy. The fairgrounds were quite large, covering almost 400 acres. The Forestry Building was one of the larger exhibits, but was also quite notable as being the only permanent edifice built for the fair. Beyond the regional focus, there were many other exhibits that characterized the expo as a true world's fair. A number of states and foreign countries housed marvelous displays, and a special section of the expo dubbed "The Trail" provided fair-goers with a variety of entertaining novelties.