The Gas Works were built in 1851 by the SilverFactory; originally it was a small plant built from a kit shipped from New York.
In 1868 it was replaced by a larger, more permanent structure, owned by a separate company, and sold gas to the new MolassesDistillery in 1870
By 1919 supplies of the feed stocks for manufactured gas (coke and illuminating oil) are starting to run short, and prices are climbing.
In the 1870s when the MolassesDistillery was founded, manufactured gas was emerging as the power source of choice (see http://www.hatheway.net/history.htm), and most towns of 10,000+ had a GasWorks.
A lot of information on Manufactured Gas is available at http://www.heritageresearch.com/manufactured_gas_A.htm (and _B, _C, etc...)