Dunne Avenue (Santa Clara County)

Dunne Avenue is an approximately fourteen-mile highway located in southeast Santa Clara County, California. The roadway begins at the western outskirts of Morgan Hill and ascends through the Diablo Range via Anderson Lake to Henry W. Coe State Park. Dunne Avenue east of Morgan Hill was originally known as Cochrane Road and later Steely Road. The roadway east of Morgan Hill was first used to access the ranch of Henry W. Coe and was substantially realigned in 1950 over Anderson Lake via the Cochrane Truss Bridge.

Part 1; the history of Dunne Avenue

What is now Dunne Avenue east of Morgan Hill was originally part of Cochrane Road. Cochrane Road east of Coyote Creek was used to access the ranching property of Heny W. Coe in the Diablo Range. Coe had acquired his ranching property in 1905 and occupied it until his death in 1943.

Cochrane Road can be seen ascending through the Diablo Range to the Coe Ranch at Pine Ridge on the 1917 United States Geological Map of Morgan Hill.

Cochrane Road east of Coyote Creek can be seen renamed as "Steely Road" on the 1935 Division of Highways Map of Santa Clara County.

Henry Coe's son sold his father's ranch to Beach Land & Cattle Company in 1948. Beach Land & Cattle Company would greatly improve Steely Road and the surrounding roads on Coe Ranch. In 1950 the Anderson Lake reservoir had been formed along Coyote Creek. The then new reservoir site required Steely Road to be realigned. Steely Road was made continuous with Dunne Avenue via a new alignment which carried it over the Cochrane Truss Bridge.

Also, during 1950 Henry Coe's daughter bought back his ranch. The ranch property was subsequently turned over to Santa Clara County during 1953. The County would repurpose the property as Henry W. Coe Park.

Steely Road can be seen realigned over the Cochrane Bridge and made continuous with Dunne Avenue on the 1955 United States Geological Map of Mount Sizer.

Henry W. Coe Park was deeded to the State of California during 1958 and became a State Park. It isn't fully clear when the Steely Road designation was dropped in favor of it being consolidated with Dunne Avenue.

Part 2; a drive on Dunne Avenue from Morgan Hill to Henry W. Coe State Park

Dunne Avenue ascends into the Diablo Range east of Morgan Hill. As Dunne Avenue approaches Holiday Drive traffic is advised that Henry W. Coe State Park is ten miles away.

Dunne Avenue crosses the Anderson Lake reservoir via the Cochrane Truss Bridge. During 2020 the reservoir was drained to allow for Anderson Dam to be demolished and rebuilt to modern seismic standards. The dam was found to be susceptible to collapse during a 6.6 magnitude or greater earthquake during a 2009 seismic study.

Dunne Avenue ascends above Anderson Lake and intersects Finley Ridge Road at 1,923 feet above sea level. The roadway narrows to a single lane after the second switchback.

Dunne Avenue continues to climb from Finley Ridge Road and terminates at the entrance to Henry W. Coe State Park. The park entrance station is located at approximately 2,700 feet above sea level.