Marshes Flat Road is named after Marsh's Flat and is one of the oldest highway corridors in Tuolumne County. This corridor originally connected Don Pedro Bar at the Tuolumne River to the original Priest Grade (now Old Priest Grade) at Moccasin Creek. The highway reportedly had a known hideout of Joaquin Murietta and provided access to the early mining community of Indian Bar.
The final descent on Marshes Flat Road to California State Route 49 is down the Kelley Grade. The Kelley Grade loses approximately 900 feet of elevation in one large three-quarter mile drop which requires usage of lower gears. Marshes Flat Road is 8.4 miles long and is almost entirely comprised of single-lane roadway.
Part 1; the history of Marshes Flat Road and the Kelley Grade
Marshes Flat Road and the Kelley Grade comprise one of the oldest highway corridors in Tuolumne County. The roadway was constructed around 1850 is named after Marsh's Flat which is located southeast of Moccasin Peak. The corridor originally permitted direct travel from Don Pedro Bar at the Tuolumne River northeast to the Priest Grade (now Old Priest Grade) via the steep descent of the Kelley Grade.
Marshes Flat Road permitted the only road access to the short-lived gold mining town of Indian Bar located on the Tuolumne River. Marsh's Flat itself is reportedly to be one of the many hiding locations used by Joaquin Murrieta during the early 1850s. These reports are unclear given the murky nature of the stories regarding the life of the famed bandit.
From Don Pedro Bar the corridor of Marshes Flat Road is shown continuing northeast to the namesake Marsh's Flat (shown as Marshall's Flat). A spur road is shown branching westward to the site of Indian Bar on the Tuolumne River.
From Marsh's Flat the corridor of Marshes Flat Road is shown descending the Kelley Grade to the Priest Grade at Moccasin Creek.
The site of Don Pedro Bar would later be submerged during construction of Don Pedro Dam. The original arch concrete dam was built near the town site along the Tuolumne River by the Modesto Irrigation District. The dam was complete by 1924 and is 283 feet high.
The original Don Pedro Dam can be seen in a 1925 era public domain photo.
Despite the flooding of Don Pedro Bar almost the entire corridor of Marshes Flat Road would remain above the water line. Marshes Flat Road would be eventually bypassed by the current corridors of California State Route 132 and California State Route 49. California State Route 49 in particular north of Coulterville was built along more favorable grades descending along Moccasin Creek.
The 1935 Division of Highways map of Tuolumne County displays the corridor of Marshes Flat Road spanning from the small community of Blanchard northeast to the company town of Moccasin at California State Route 49.
The 1944 Unites States Geological Survey map of Merced Falls displays Marshes Flat Road beginning at Blanchard. The map displays early California State Route 132 following what is now Granite Creek Road.
The 1948 United States Geological Survey map displays Marsh's Flat being located at 1,862 feet above sea level.
The same map displays the Kelley Grade beginning at 1,812 feet above sea level at Marsh's Flat and ending at 936 feet at California State Route 49 near the Moccasin Reservoir.
During the winter of early 2023 two culverts on Marshes Flat Road at First Creek and Second Creek were damaged by storms. Water can be seen overtopping the roadway as seen on the Facebook page of Jim Hall. Similar winter storm damage had occurred at both culverts in 2023.
During late 2024 Tuolumne County contracted to have the culverts at First Creek and Second Creek replaced. The modern culverts were completed during December 2024 and were featured on the Tuolumne County Public Works Department Facebook page on February 18, 2025.
Part 2; a drive on Marshes Flat Road and the Kelley Grade
From eastbound California State Route 132 traffic is advised Moccasin can be reached via Marshes Flat Road.
To reach Marshes Flat Road traffic must follow the original alignment of California State Route 132 along Granite Springs Road.
Northbound Marshes Flat Road begins at the site of Blanchard at the intersection of Blanchard Road and Azucena Court. Blanchard Road itself branches away from Granite Springs Road.
Upon beginning Marshes Flat Road narrows to a single lane and passes through a cattle guard.
Marshes Flat Road continues north to a portion of the Don Pedro Reservoir along Hatch Creek.
Marshes Flat Road passes through a switchback at First Creek.
Marshes Creek Road climbs to another switchback at Second Creek.
Marshes Flat Road from Second Creek continues to ascend along the course of Hatch Creek. As the roadway approaches Rodina Drive it passes a private land parcel filled with vintage car parts.
Marshes Creek Road makes one final climb and enters Marsh's Flat.
Marshes Flat Road passes through the namesake Flat and approaches the Kelley-Grade. Truck traffic is warned to use lower gears through the steep descent.
Marshes Flat Road makes the drop through the Kelley Grade to California State Route 49 near the San Francisco owned company town of Moccasin. The penstock carrying water from Hetch Hetchy in Yosemite National Park to the Moccasin Powerhouse is easily visible from the Kelley Grade. The Moccasin Powerhouse was made operational in August 1925. The incline of the Kelley Grade appears to briefly approach 10%.
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