A 1.5-acre vegetation fire burned through brush and timber on Hillside Avenue in Mill Valley on Monday, July 27, prompting a shelter-in-place before firefighters halted its spread. No one was injured. No structures were damaged.

The Southern Marin Fire District, the Mill Valley Police Department and mutual aid agencies responded at approximately 4:42 p.m. to the fire in the 300 block of Hillside Avenue, north of East Blithedale Avenue and just south of Mayor's Lookout, according to the Mill Valley Police Department and CBS San Francisco.

By 5:33 p.m. the fire had grown to about 1.5 acres. The Southern Marin Fire District reported that the blaze had a slow rate of spread, burning through previously treated vegetation, which allowed crews to gain the upper hand quickly.

Firefighters stopped the fire's forward progress by approximately 6:24 p.m., according to the Fire District.

No evacuations were ordered, the Mill Valley Police Department said. Authorities did issue a shelter-in-place for the immediate area and asked the public to stay away so emergency crews could work.

After containing the fire, crews established a hose line around the perimeter. Firefighters planned to remain on scene for several hours to patrol, extinguish hot spots and strengthen containment lines, the Fire District said.

The cause of the fire remains under investigation, according to the Mill Valley Police Department.

The blaze arrived less than two weeks after PG&E shut off power to more than 2,000 meters in the Mill Valley area on Wednesday, July 15, as a wildfire safety measure during hot, dry and windy conditions. That shutoff, which affected about 2,018 households in Blithedale Canyon, Cascade Canyon, Middle Ridge and Muir Woods Park, was the first in Marin County since at least 2021, according to PG&E's post-season reports to the state.

Mill Valley sits in what fire professionals call the wildland-urban interface. Marin County Fire Chief Jason Weber said at a May 2 public forum that the southern Marin zone has steeper terrain, heavier fuels and narrower roads than most of the county.

The Southern Marin Fire District conducts more than 4,400 home defensible-space inspections per year across its coverage area, with roughly 1,500 of those in Mill Valley.

The Greater Mill Valley Fuel Break project, which aims to encircle the city with 11 to 13 miles of continuous treated perimeter, has reached approximately 70% of its linear treatment goal as of summer 2026, covering 673 acres.

Residents with information about the fire's cause can contact the Mill Valley Police Department or the Southern Marin Fire District.