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Cape Cod Salt Works: Harnessing Renewable Energy in the 19th Century

Brian Morris/WCAI

Salt works once were a common sight along Cape Cod shores. Today, a replica of a salt works sits on the grounds of the Aptucxet Trading Post in Bourne.

Salt was in constant demand for colonists who came to the new world from England in the 1600s. It was mainly used to preserve food, and the colonists got much of their supply of salt from England. But they wanted to figure out how to make it themselves. Initially, they tried filling cast-iron kettles with water.

“They’d build a fire under it, and it really was the beginnings of providing salt for the colonists,” said Marth Beth Ellis, a volunteer at Aptucxet. “It would take a great deal of time for the water to evaporate, and it would leave crystals of salt all along the inside of that kettle. And they would have to scrape it off, and the result was not a lot of salt.”

Credit Brian Morris/WCAI
Mary Beth Ellis is a volunteer at the Aptucxet trading Post in Bourne, where the salt works replica is located.

The process also used up a lot of valuable lumber. By the 1770s, the colonists were fighting for their independence from the Crown. They also wanted to break their dependence on England for their supplies of salt. 

“The Continental Congress in the 1770s put out a plea to all those who lived along the shore. They needed to find a way to extract salt efficiently from the coast,” said Ellis.

A financial reward was promised to anyone who could come up with a workable method. Captain John Sears of Dennis believed he could. 

“He was known as ‘Sleepy’ John Sears, because he was always thinking. He was always trying to figure out ways to do things. And he would wander along the coast just looking about and trying to figure out what would work. What he came up with was a design that actually did work,” said Ellis.

Sears devised a mechanism of large wooden vats that held seawater, which would be evaporated by the sun to extract the salt. But rainwater could ruin the process, so Sears devised a system of wooden roofs set on rollers that could be rolled back on sunny days, and then rolled over the vats of evaporating seawater to protect them from the effects of rainfall. When rain was predicted, it was the equivalent of a snow day today.

Credit Brian Morris/WCAI
Each salt works had a roof set on wooden rollers, which could be rolled over the vats of evaporating saltwater when it rained, then moved out of the way on sunny days.

“The school bells would ring, the kids would be let out of school, the teachers and the children would go to the nearest salt works and help roll the roofs,” said Ellis.

Captain Sears’ design was not an instant success. That first season, he only extracted eight bushels of salt. Seawater would be carried by hand, bucket by bucket, from the shoreline up to the vats – a slow, labor-intensive process. But Sears eventually hit on a way to improve the efficiency of the operation.  

“He literally stumbled upon a bilge pump from a ship and realized that he could also harness wind power to a small windmill to pump the water in, which would make it possible for him to do it quicker,” said Ellis. “And at the end of that first season using that, he had 30 bushels. So there was a huge increase with the use of the wind power.” 

Eventually, there were numerous salt works along the coast of Cape Cod. Those are all long gone, but in 1967, students from the Upper Cape Vocational Tech School in Bourne constructed the salt works replica, which offers visitors a glimpse of the former salt-making process.

Salt works began to decline around the 1830s. Salt springs were discovered in New York state, providing access to large new deposits of salt. And the newly-built Erie canal allowed for easier transport.

As the salt works around Cape Cod were dismantled, much of their lumber was re-purposed to build local houses. 

“They were recycling, re-purposing whatever they had, and they were using solar evaporation and wind power to do what they needed to do to survive,” said Ellis.