The Hotel Belmont was the first noteworthy building to stand atop Crown Hill, the present site of Belmont High School. Eventually, the hotel was abandoned, and later it was transformed into the private Belmont School for Girls. After the school was destroyed by fire, the grounds were left vacant, except for five oil wells and a pumping plant. On February 28, 1921, the Los Angeles Board of Education purchased the site for $100,000, for the purpose of constructing Belmont High School.

Belmont opened its doors on September 11, 1923, to about 500 students, all sophomores, and 28 faculty members. Most of the school's traditions were created by those pioneer students during the first months of the school's existence. The school newspaper conducted an election to select its name, with "Sentinel" easily winning over "Progress." To this day, Belmont's students are known as Sentinels. Those first students favored “Sentinels" because they were able to oversee the entire city from their "lookout" on Crown Hill. In another election, the school's colors, green and black, were selected over brown and white.

Notable Belmont Alumni:

Ron Botchan, NFL Official
Richard Crenna, actor
Brad Dexter, actor
Levon Chaloukian, President, Academy of Television Arts & Sciences
Craig Ellwood, architect
Mike Frankovich, film producer
Luis (Lou) Gomez, MLB player
Young-Oak Kim, highly decorated combat veteran
Ricardo Montalban, actor
Anthony Quinn, actor
Mort Sahl, humorist
Mike Stoller, songwriter
Jack Webb, producer, director, actor
Jack Smith, journalist
Robert Lyles, NFL player
Sidney Thompson, LAUSD Superintendent
Ralph Lazo, activist
Sal Castro, activist (faculty)
Tony Feliz, musician (faculty)
Dentler Erdmann, educator (faculty)
Tom Arima, educator/coach