On this day in 1994, an earthquake rocks Los Angeles, California, killing 54 people and causing billions of dollars in damages. The Northridge quake (named after the San Fernando Valley community near the epicenter) was one of the most damaging in U.S. history.

It was 4:31 a.m. when the 6.7-magnitude quake struck the San Fernando Valley, a densely populated area of Los Angeles located 20 miles northeast of the city’s downtown. With an epicenter 12 miles beneath the earth’s surface, the earthquake caused the collapse of several apartment buildings. At the Northridge Meadows complex, 16 people died, all of whom lived on the first floor, when the weak stucco structure fell down on them as they slept.

Given the strength and location of the earthquake, it was fortunate that the death toll was not far higher. Two key factors were critical in reducing the casualties. First, the quake struck in the middle of the night while nearly everyone was at home in their beds. A mall parking lot in the Valley collapsed, but no one was killed because it was entirely empty. Several highways also suffered critical failures, but only one police officer died, when his vehicle plunged off an overpass. The other key factor was that the city’s building and safety codes were strengthened following the 1971 Sylmar quake that collapsed the San Fernando Veterans Hospital. Every building constructed after the new regulations were implemented stayed intact.

Still, the quake caused a huge amount of property damage over a wide area, especially in the beach community of Santa Monica, even though it was relatively far from the epicenter. As much of Santa Monica stands on soil that is less solid than bedrock, it suffered severe ground movement during the earthquake. The partial collapse of the Santa Monica freeway snarled traffic in Los Angeles for months. All told, it is estimated that the earthquake was responsible for $20 billion in damages.