Mount Tamalpais is the highest peak in the Marin Hills, which are part of the Northern California Coast Ranges. The elevation at the East Peak, its highest point, is 2,571 feet (784 m). The West Peak, the mountain’s second highest peak where a radar dome currently stands, is 2,560 feet (780 m). It stood over 2,600 feet (792 m) before the summit was flattened for the radar dome construction. The mountain is clearly visible from the city of San Francisco and the East Bay region.

The majority of the mountain is contained in protected public lands, including Mount Tamalpais State Park, Muir Woods National Monument, and the Mount Tamalpais Watershed. It adjoins the Golden Gate National Recreation Area (which in turn adjoins Point Reyes National Seashore) as well as several Marin County Open Space Preserves. This provides nearly 40 miles (64 km) of continuous publicly accessible open space. Some of the lower slopes of Mount Tamalpais fall within several cities and unincorporated communities of Marin County, including Mill Valley, Tamalpais-Homestead Valley, Stinson Beach, and Kentfield. These areas are generally developed, consisting of mostly low-density single-family homes.
Like the rest of the California Coast Ranges, Mount Tamalpais is the result of uplift, buckling, and folding of the North American plate as it slides along the Pacific Plate near the San Andreas fault zone.

In 2004 it was suggested that a blind thrust fault, like the one that caused the infamous Northridge earthquake, lies beneath Mount Tamalpais. This idea was partly based on the steepness of Mount Tamalpais and of nearby Bolinas Ridge, such steepness on the visible surface often being the result of blind thrust faults. Another reason for the suggestion was that the San Andreas Fault creeps more slowly, south of Mount Tamalpais, than it does in its sections north of Mount Tamalpais and in the Olema Valley, and the existence of a blind thrust fault may explain the different creeping velocities. If a blind thrust fault does exist under Mount Tamalpais, and if it ruptures, it could be potentially devastating to the North Bay, San Francisco, and any other nearby locale resting on unstable earth and loose fill.

Major Mount Tamalpais rockforms include serpentine, particularly evident in outcroppings near the summit and on the north side. A number of serpentine endemic plants grow in the serpentine soils in this part of the mountain.
With its height, various faces, and proximity to the ocean and bay, the mountain contains many micro climates, ranging from cool and foggy in lower ocean-facing valleys with their redwood forests, to hot and dry on the Manzanita slopes, cool and breezy at the summit, and shady on the heavily Douglas-fir-forested north slopes near Alpine Lake.

Annual precipitation around Mount Tamalpais varies greatly from around 27.5–31.5 inches (700–800 mm) in the drier, eastern foothills to about 59 inches (1,500 mm) near the Bolinas Ridge, close to the Pacific Ocean. Both Mount Tamalpais and the Bolinas Ridge force moisture out of the air efficiently, since the air is cooled rapidly as it ascends the steep mountain faces and thus Mount Tamalpais’s western part is heavily forested with tall redwoods and Douglas firs. The same fact holds for the steep, south-facing bowl canyon that Muir Woods is located in, with precipitation in Redwood Canyon at around 39.4–47.2 inches (1,000–1,200 mm).
As in San Francisco, most of the annual precipitation falls during the winter months. During cold, wet winter storms, the mountain also regularly gets some snowfall, sometimes as much as 6 inches (15 cm) overnight, as observed in February 2001, March 2006, and February 2011. The region sometimes gets hit with strong Pacific storms that may topple trees, and bring hurricane force winds to exposed, barren areas like the Bolinas Ridge and the summit of Mount Tamalpais. In summer, the area gets almost no precipitation, except for fog drip that occurs in Muir Woods, the Bolinas Ridge and the western end of Mount Tamalpais, where summer fog and oceanic breezes are more prevalent. In contrast, the eastern foothills, sheltered from the oceanic breezes and fog, are drier, since the foothills force little moisture out of the air. This leads to the fact that the eastern slopes contain only oak, pine, shrub, woodland, and sparse Douglas-fir forest.

Temperatures on top of Mount Tamalpais are generally somewhat cooler than places next to the San Francisco Bay or the ocean due to elevation. In summer, however, the top of Mount Tamalpais may actually be warmer than the middle, foggy elevations due to a thermal inversion. The summer fog and breezes make locations on Mount Tamalpais closer to the ocean cooler than the blazing hot interior valleys.
ardwood woodland types are generally subtypes of California oak woodland, including oak-bay-madrone forest, oak woodland, and oak savannah. Oak-bay-madrone forests are found in areas with moderate moisture and particularly favor north-facing slopes. They are dominated by one or more of three hardwood tree species – Coast Live Oak, California bay, and Madrone. Coast live oak tends to be dominant in somewhat drier areas, while bay is more dominant in shadier, moister areas; Madrone is abundant in certain soil types in both moist and dry spots. Oak woodlands are a more open-canopy forest dominated by coast live oak, while oak Savannah has a completely open canopy and represents a mixture of coast live oak woodland and grassland.

The great diversity of microclimates on Mount Tamalpais ensures a wide variety of plant communities as well. Plant communities on the mountain include various types of hardwood and coniferous forests, coastal scrub, chaparral, grassland, and wetland vegetation. Wholly or partially coniferous forest types are found in the moistest areas of Mount Tamalpais. Coast redwood forests are restricted to areas where the particular ecological needs of redwood are met: areas characterized by high overall moisture, low elevations below the fog line, and deep soils. Muir Woods is the most extensive and best-known redwood forest of the Mount Tamalpais area. Mixed evergreen forests of various combinations of tanoak, madrone, coast and canyon live oak, and Douglas-fir are found in moist areas on middle to high elevations on the mountain. Very moist areas of mixed evergreen forest may also include bay, redwood, and California torreya. Areas in which mixed evergreen forests are predominant include areas of Fairfax-Bolinas Road and Ridgecrest Boulevard and around Alpine Lake.
Various kinds of scrub communities are also widespread. Low-elevation areas below the fog line with relatively low overall rainfall or thin soils are often the site of a northern coastal scrub community characterized by coastal sage-coyote brush association, with lesser amounts of poison-oak, bush monkeyflower, California blackberry, western bracken fern, and various species of grasses and forbs. Chaparral is predominant in areas characterized by thin, rocky soils and little moisture. Two main types of chaparral are found the mountain chamise chaparral and manzanita chaparral. Chamise is dominant in the hottest, most xeric areas of the mountain, particularly on south- and west-facing slopes, while manzanita is dominant in other xeric areas, particularly on east-facing slopes and forest borders. Areas of mixed chamise-manzanita chaparral occur in relatively more mesic areas; Ceanothus and dwarfed interior live oak may also predominate on such sites. Areas in which various kinds of chaparral communities are dominant include areas along Old Railroad Grade.

Grassland areas are also common on Mount Tamalpais. Native perennial bunchgrass species were originally dominant, but most of these grasslands are now dominated by invasive annual grasses of European origin. Native grasslands, still found in a few isolated areas, are of two types. Northern coastal prairie is found below the fog line and is characterized by a Festuca-Danthonia association, while valley grassland, found in drier areas, is dominated by Nassella pulchra, with Elymus glaucus and Leymus triticoides also being common.
Dying pine tree near the summit of Mount Tamalpais

Wetland vegetation types found on Mount Tamalpais include coastal riparian forests, wet meadows, and some marsh areas. Coastal riparian forest is predominant along the valley streams of Mount Tamalpais. Red and white alder (Alnus rubra and Alnus rhombifolia) and arroyo and yellow willow (Salix lasiolepis and S. lasiandra) are dominant in these types of woodland, with bigleaf maple (Acer macrophyllum), box-elder (Acer negundo ssp. californicum), and California bay also being common. Wet meadows are present in several high-elevation spots on the mountain, while High Marsh represents a rare example of a marsh community on the mountain.
Serpentine soils have a high rate of endemism and are the site of several unique subtypes of the above plant communities. Serpentine grasslands are some of the few grasslands in which native perennial grasses are still relatively dominant. Serpentine chaparral forms a unique plant community, dominated by dwarfed leather oak (Quercus durata), Jepson ceanothus (Ceanothus jepsonii), Tamalpais manzanita (Arctostaphylos montana), and Sargent cypress (Cupressus sargentii). On the upper slopes of the mountain, small groves of Sargent cypress trees up to 50 feet (15 m) tall can be found in serpentine areas.

Several species of endemic plants are found only on serpentine soils; these species may be widespread, but only occur on serpentine soils, or the may be more restricted, only growing in a few other places besides Mount Tamalpais, or may even be restricted just to Mount Tamalpais. The Mount Tamalpais thistle (Cirsium hydrophilum var. vaseyi), for example, is a rare variety of thistle known only from the serpentine seeps of the mountain. The Mount Tamalpais jewelflower (Streptanthus batrachopus) is also limited to the area.
The name Tamalpais was first recorded in 1845. The meaning of the name is not well-established and there are several versions of the etymology of the name. One version holds that the name comes from ostensibly Coast Miwok words for “coast mountain” (tamal pais). Another holds that it comes from the Spanish Tamal pais, meaning “Tamal country,” Tamal being the name that the Spanish missionaries gave to the Coast Miwok peoples. Yet another version holds that the name is the Coast Miwok word for “sleeping maiden” and is taken from a “Legend of the Sleeping Maiden.” However, this legend actually has no basis in Coast Miwok myth and is instead a piece of Victorian-era apocrypha.
The Coast Miwok are said to have believed that an evil witch dwelled at the top of Mount Tamalpais and therefore never set foot on the peak. However, it has been said the Miwoks did this in order to keep settlers off the sacred mountain.

Tamalpais was home to the Mount Tamalpais and Muir Woods Railway, also known as “The Crookedest Railroad in the World,” a railroad which meandered its way up to the peak from downtown Mill Valley until a road was constructed to the peak, and automobiles gained popularity. The 8-mile standard-gauge railroad required geared steam locomotives and operated from 1896 to 1930.

Early wireless towers were constructed on the mountain in the early 20th century, only to be destroyed by one of the periodic hurricane-force windstorms.

The U.S. Weather Bureau operated a weather station at the site of the now defunct Mill Valley Air Force Station for many years.

The peak and its surrounding areas are the birthplace of mountain biking in the 1970s, where early mountain bikers such as Gary Fisher, Charlie Kelly, and Joe Breeze were active.

British philosopher Alan Watts owned a Cabin on Mount Tamalpais later in his life, where he ultimately died in his sleep of heart failure on November 16, 1973 .

Mt. Tam Photos & Artwork