1. In 1804, Spanish explorer Juan Bautista de Anza led a group of settlers, along with soldiers and livestock, from Santa Fe, New Mexico to San Francisco (then known as Yerba Buena). This expedition arrived in what is now California on August 17th, marking a significant moment in early California history.

2. In 1915, the Panama-Pacific International Exposition opened in San Francisco. This World's Fair celebrated the city's recovery from the devastating earthquake and fire of 1906 and showcased new innovations and technologies. The fair ran from February to December of 1915, but August 17th was designated as "California Building Day" to highlight the state's contributions to the Expo.

3. On August 17th, 1896, gold was discovered in the Klondike region of Yukon, Canada. This event sparked the Klondike Gold Rush, which brought thousands of fortune-seekers to California and other western states in search of riches. Many of these prospectors passed through San Francisco on their way to Alaska, leaving a lasting impact on the city's economy and culture.

4. The first transcontinental telephone call was made on August 17th, 1915. The call was placed between San Francisco and New York City, marking a significant milestone in telecommunication history. The call was made possible by the completion of a multi-year effort to lay a transcontinental telephone line across the United States.

5. In 1998, President Bill Clinton designated the California Coastal National Monument, which spans 1,100 miles along the state's coastline, as a national monument. This protected area includes numerous offshore rock formations, sea stacks, and islands that are home to a variety of wildlife, including seabirds, marine mammals, and rare plant species. August 17th is now recognized as "California Coastal National Monument Day" to celebrate this important natural resource.