Near the main entrance to the University of California, Santa Cruz lies the Cowell Lime Works Historic District.
Lime was an essential building material in late 19th century California, and Santa Cruz was at that time one of the state’s most important lime-producing regions. Limerock was fired in giant kilns to convert it into lime, which was a key ingredient in mortar, plaster, whitewash, and many other industrial products.
Santa Cruz lime had a reputation for being of fine quality. It helped build San Francisco in the decades after the Gold Rush. It was also shipped to other cities up and down the California coast, inland to Sacramento and the San Joaquin Valley, north to Oregon, and even to Hawaii.
Cowell Lime Works
The Cowell Lime Works Historic District preserves the most intact 19th century lime manufacturing facility in California.
A succession of companies operated here. The first to make lime on a large scale was the firm of Isaac E. Davis and Albion P. Jordan starting in 1853. In 1865 Henry Cowell bought A. P. Jordan’s half of the business and, in 1889, Davis’s share. Cowell, and later his sons, ran lime-making operations at this and three other nearby locations in Santa Cruz County. They also made lime in the Sierra foothills and in Washington state. The last of Cowell’s Santa Cruz County kilns, beside Highway 9 in what is now Henry Cowell Redwoods State Park, ceased operation in 1946.
Lime Kilns (Pot Kilns)
These giant stone kilns were the heart of the lime-manufacturing operation. The three kilns on the left are pot kilns (aka batch kilns or intermittent kilns). The interior of each measures about 11 x 33 x 15 feet high. The front walls are about 6 feet thick, and each kiln has four doorways at the bottom. The kiln on the far right is a continuous kiln (see separate stop).
Chunks of limerock were loaded into the top of each pot kiln, and the lumps of finished lime were removed through the doorways at the bottom. It took the workers approximately 2 days to load a kiln, 5 days to fire, 2 days to cool, and 2 days to unload.
The limerock had to be held at around 1,800˚F to convert it to lime. The workers had no instruments in those days to exactly measure the temperature. They had to judge by the color of the fire and the look of the rock to know when it was done. This took years of experience. If the rock was cooked too much, it turned into “dead-burnt” lime and was useless (would not mix with water). If it was not cooked enough, a core of unconverted limerock would remain hidden in the center, and customers would gripe that they were cheated.
For those of you who want to know the chemistry, the rock is made of calcium carbonate, CaCO3. The heat drives carbon dioxide, CO2, gas out of the rock, leaving calcium oxide, CaO, which is the lime.
Each kiln produced over 1,000 barrels of lime per burn. The pot kilns were incredibly inefficient, and consumed between 75 and 150 cords of split redwood as fuel for each load.
By having three kilns, each at a different stage of production, the plant could produce a near continuous supply of lime. These kilns were remodeled in the 1890s and were in operation until around 1920.
Take the Self-Guided Mobile Tour
This piece is part of UCSC Lime Kilns Tour by Frank Perry on behalf of The Friends of the Cowell Lime Works Historic District. Download the free app with many tours of the Santa Cruz area and beyond.
The content for the AppTour was prepared by The Friends of the Cowell Lime Works Historic District, University of California, Santa Cruz, and is © 2015 by The Friends. Much of the information is from the book, Lime Kiln Legacies: The History of the Lime Industry in Santa Cruz County. The book can be purchased at the Museum of Art and History in person or on-line. It’s also available through Amazon.com.
During this tour you will see that some of the historic buildings have been put to modern uses by the University. Others remain unused but are gradually being restored with private gifts of funding and materials. For more information on how to help, contact the Friends of the Cowell Lime Works Historic District. This UCSC friends group is dedicated to researching, preserving, and teaching about the history of this historic site.
- Lime Kiln Legacies: The History of the Lime Industry in Santa Cruz County, by Frank A. Perry, Robert W. Piwarzyk, Michael D. Luther, Alverda Orlando, Allan Molho, and Sierra L. Perry. Published by the Santa Cruz Museum of Art and History; 2007.