Mt. Wilson is a 5,712′-high mountain in Los Angeles County, and seems to have been a very popular early-20th century destination for hikers if the number of vintage snapshots taken there is any indication. According to this website, the first modern trail up the mountain — transforming an old Indian path — was built in 1864, and by the 1880s “up to 70 hikers and horse-riders [would] climb the trail to camp at Mt. Wilson on weekends, building huge bonfires at the peak to signal their safe arrival.”
The names written on the back of this shot are “Davis” and what looks like “Goodan” — should anyone in the area have any inkling of who they perhaps were.