The peak was surrounded by heavy smoke as firefighters tried to create defensive space between the flames and the iconic Mount Wilson Observatory.
The mountain is also home to an estimated $1 billion worth of transmission towers, a key site for TV, radio and government agencies.
Mount Wilson has been threatened several times in the past two weeks, but each time firefighting efforts and weather conditions helped prevent significant damage.
Winds were blowing Monday night around 5-10 mph near the peak and fire officials described the fire as making a "hard push" toward Mount Wilson.
RELATED: Bobcat Fire crews race to protect Mount Wilson
The Mount Wilson Observatory played a key role in advancing 20th century astrophysics since it was founded in 1904.
Mount Wilson Institute employees already evacuated last week, leaving dozens of firefighters on site to protect the landmark
We give our sincerest thanks to the firefighters who are on the ground defending our observatory as well as the pilots flying aircraft for fire suppression. Here’s a picture from of firefighters crossing the "Einstein Bridge" from the 100-inch dome. #BOBCATFIRE pic.twitter.com/yrbLPtnhJh— Mount Wilson Observatory (@MtWilsonObs) September 15, 2020
Mount Wilson invested in a fire suppression system following the 2009 Station Fire, rebuilding a half-million-gallon water tank with 33 places for the remaining 12 engine companies to access water.
There are also new high-pressure fire hydrants.
Mount Wilson staff says they haven't slept in days watching the fire creep closer to the 5,700-foot-high peak.
"This is a world-significant institution in terms of its instruments, the telescopes, the people who work there, the scientific endeavor that was accomplished there," said Tom Meneghini, executive director of the Mount Wilson Institute.
"This is where astrophysics was invented. It was done on Mount Wilson. The first half of the 20th century was about Mount Wilson. It was the only place in the world where you could do that type of science."