1. California officially became a state on January 1, 1850. The state's admission into the Union was a significant event in American history, as it helped to solidify the country's expansion westward. California's population boom during the Gold Rush of 1849 helped to push the state's admission into the Union.

2. The Tournament of Roses Parade is held annually on January 1 in Pasadena, California. The parade has been a longstanding tradition in the state, dating back to 1890. It features elaborate floats, marching bands, and equestrian units, and culminates with the Rose Bowl football game.

3. On January 1, 1914, the world-famous Mission Inn Hotel in Riverside, California held its grand reopening. The hotel, which had been in operation since the late 19th century, had undergone a massive renovation and expansion, becoming one of the largest hotels in the world at the time.

4. In 1934, the Golden Gate Bridge and Highway District was created on January 1. The district was tasked with overseeing the construction and maintenance of the iconic Golden Gate Bridge, which officially opened in 1937. Today, the bridge is one of California's most famous attractions, drawing millions of visitors each year.

5. On January 1, 1990, the landmark Americans with Disabilities Act (ADA) went into effect in California and throughout the United States. The ADA was a groundbreaking piece of legislation that provided protections and accommodations for individuals with disabilities, and has been instrumental in helping to create a more inclusive and accessible society.