Siskiyou County is home to one of the more interestingly named Sign County Routes in California; County Route A12 the 99-97 Cutoff.
County Route A12 ("A12") is a 17.90 mile Sign County Route completely contained with Siskiyou County. A12 is aligned between former US Route 99 ("US 99") near Grenada and US 97 to the east near the foot of Mount Shasta. A12's designation of 99-97 Cutoff denotes that it was meant to serve a connector route between US 99 and US 97. Despite US 99 no longer existing as a State Highway the routing of A12 still begins at it rather than Interstate 5 ("I-5"). The below image from cahighways.org displays the route of A12.
Part 1; the history of Siskiyou County Route A12
What is now A12 consists of what was the road east of former US 99 connecting Grenada to the community of Mayten. A road east of Mayten to US 97 existed before 99-97 Cutoff but was primitive compared to the modern A12. This older highway can be seen on the 1935 Division of Highways Map of Siskiyou County.
The opening of 99-97 Cutoff is discussed in detail in the March/April 1955 California Highways & Public Works. The construction of 99-97 Cutoff was a Federal Aid Secondary ("FAS") project which helped Siskiyou County fund construction of a modern highway.
The history of 99-97 Cutoff is discussed in great detail in the March/April 1955 California Highways & Public Works. The corridor of 99-97 Cutoff is described as being explored by Hudson Bay Company trappers in 1833. By 1852 surveyors were attempting to plot a path through what was the future corridor of 99-97 Cutoff but were killed by local Tribes. By 1855 the future corridor of 99-97 Cutoff was first used by a wagon train as en route to Yreka. The corridor of future 99-97 Cutoff was popular with settlers due to the presence of the easy to identify Sheep Rock. In 1856 the future corridor of 99-97 Cutoff began to be traveled by Stage Lines and appears to have been an early example of a Franchise Toll Road. By 1857 the future corridor of 99-97 Cutoff came to be known as the "Pit River Road" but in time would be more commonly known as the "Shasta Valley Route." In the mid-1880s Grenada had been established as a siding of the Southern Pacific Railroad on the Shasta Valley Route. The siding of Grenada renewed interested in the Shasta Valley Route which became a Siskiyou County public highway in the late 1880s. The Shasta Valley Route remained an unsurfaced highway until Siskiyou County undertook efforts to pave it in the 1940s. A realignment effort of the Shasta Valley Route began in 1947 and eventually became the FAS project known as 99-97 Cutoff.
Sheep Rock can be seen as a major way point east of Yreka on the 1857 Britton & Rey's Road Map of California.
According to cahighways.org 99-97 Cutoff was added to the Sign County Route program in 1959 when it was given the designation of "A12." As noted above despite US 99 functionally ceasing exist the western terminus of A12 was never truncated to I-5. As of November 2011 A12/99-97 Cutoff was designated the "Veterans Memorial Highway" by the Siskiyou County Board of Supervisors to honor Siskiyou County Veterans.
Part 2; a drive on Siskiyou County Route A12
From I-5 northbound one can access A12/99-97 Cutoff via Exit 766 in Grenada. As noted above the origin point of A12 is actually slightly west of I-5 at Old Highway 99.
A12/99-97 Cutoff eastbound passes through Grenada. A12 crosses the Union Pacific Railroad and intersects A28 at Montague-Grenada Road. Big Springs is signed as 7 miles away on A12/99-97 Cutoff eastbound.
Approaching Salvador Road A12/99-97 Cutoff skirts the southern banks of Salt Lake. Salt Lake is part of a group of small lakes known as the Lava Lakes.
A12/99-97 Cutoff eastbound passes through the community of Big Springs and intersects A29 at Big Springs Road. Big Springs Road is where the former Shasta Valley Route would have diverged from modern 99-97 Cutoff. US 97 is signed as 12 miles away on A12/99-97 Cutoff from Big Springs Road.
From Big Springs A12/99-97 Cutoff turns southeast towards Sheep Rock and US 97. Approximately a half mile east of Harry Cash Road one can find the turn off for Pluto's Cave on A12/99-97 Cutoff. Pluto's Cave is a partially collapsed lava tube which was discovered in 1863.
A12/99-97 Cutoff eastbound terminates at US 97 at the foot of Mount Shasta.
An overlook Mount Shasta can be found about a half mile north of the terminus of A12/99-97 Cutoff on US 97. Mount Shasta is a stratovolcano and dominates much of the view on a clear day throughout Siskiyou County. Mount Shasta lies at an elevation of 14,179 feet above sea level and is the second highest peak in the entire Cascade Mountain Range only to Mount Rainier.
For perspective on the scale of Mount Shasta it can be seen dominating the terrain around Shasta Valley from the air.