December 21 is an important date in California history for various reasons. From significant events to notable people's birth or death, here are five interesting facts about December 21 in California history.

1. California's first gas company was established on December 21, 1852.
On this day, San Francisco Gas Company, California's first gas company, was established. The company provided gas and lighting services to San Francisco's residents and businesses, contributing significantly to the city's growth and development.

2. Baseball Hall of Famer, Lefty Gomez, was born on December 21, 1908.
Vernon Louis "Lefty" Gomez, a legendary pitcher for the New York Yankees, was born in Rodeo, California, on December 21, 1908. He played for the Yankees from 1930 to 1942 and earned a reputation as one of the best pitchers of his time, helping the team win seven World Series championships.

3. California passes the country's first-ever Clean Air Act on December 21, 1947.
On December 21, 1947, California became the first state in the country to pass a Clean Air Act. The Act aimed to regulate air pollution from industrial and commercial sources and improve the air quality across the state.

4. The controversial documentary, The Thin Blue Line, was released on December 21, 1988.
The Thin Blue Line, a documentary film about a man wrongly convicted of murder, was released in California on December 21, 1988. The film received critical acclaim and was a turning point in the genre of documentary filmmaking.

5. California Governor Jerry Brown commutes 127 sentences on December 21, 2018.
On December 21, 2018, California Governor Jerry Brown made headlines by commuting the sentences of 127 people who were serving time in state prisons. The decision was hailed as a significant move towards prison reform and reducing the state's overcrowded prison system.

In conclusion, December 21 is a significant date in California history for various reasons. From establishing the first gas company to passing the country's first-ever Clean Air Act, the day has witnessed many notable events and people's birth or death, making it an interesting day to remember.