1. On May 11, 1893, the World's Columbian Exposition opened in Chicago, Illinois. The exposition was a celebration of the 400th anniversary of Christopher Columbus' arrival in the New World and featured exhibits from countries around the globe. Washington State had its own exhibit, showcasing its natural resources and industries.

2. May 11, 1910, saw the dedication of the John Landon Memorial (also known as the Landon School) in Washington, D.C. The school was originally built as a private residence in 1832 and later purchased by John Landon, who converted it into a school for boys.

3. In 1935, on May 11th, the Works Progress Administration (WPA) began construction on the Grand Coulee Dam in eastern Washington. The dam, which was completed in 1942, provided hydroelectric power to the region and helped irrigate farmland.

4. On May 11, 1978, Seattle's iconic Space Needle was designated as a historic landmark by the Seattle Landmarks Preservation Board. The Space Needle, which was built for the 1962 World's Fair, is one of Seattle's most popular tourist attractions.

5. May 11, 2016, marked the signing of a landmark agreement between the Yakama Nation and the U.S. Forest Service to manage and protect the Columbia River Gorge National Scenic Area. The agreement recognized the Yakama Nation's cultural and historical ties to the region and ensured their involvement in the management of the area.