This building has been called the blacksmith shop, freezer barn, generator barn, and a barn-utility building. It was probably constructed in the early 1870s and housed the original blacksmith shop and other workshops and utility areas. It was originally twice the size with two side-by-side, gable-roofed sheds, the western one sheltering the More's massive matanza boilers.

In 1876 a drought brought on the collapse of the wool market in California, resulting in a matanza (Spanish for "slaughter")in which thousands of sheep were killed for their tallow. The island had been supporting up to 45,000 sheep, thousands of which would starve and, as a commodity, would go to waste. The events attracted the attention of the Santa Barbara press, resulting in an article describing the spectacle:

"The slaughter of sheep for their pelts and tallow on Santa Rosa Island is still going on and will continue for some time. 25,000 sheep are to be killed, which will leave from 15,000 to 20,000 on the island. The matanza works erected by the firm are said to be among the largest and most complete on the coast. The kettles are of enormous size, large enough to take in several hundred sheep at a time. The number of carcasses boiled daily averages about 1,200. The fires are kept burning from Monday morning to Saturday evening. The sheep are skinned, the intestines taken out and the carcasses thrown into the kettles. After going through the kettles, the carcasses are thoroughly mashed up, the bones being softened so they will pulverize under the pressure of the hand. The offal is fed to hogs. In consequence of the sheep not being very fat in this year of short feed, the amount of tallow from each sheep is comparatively small; still under this systematic mode of treatment, a fair price, considering the year, can be realized per head. The skins are salted, dried and packed for market. These operations require a large force of men."

Sometime after 1948 ranch crews removed the western structure, leaving the boilers exposed to the elements.
The remaining building was used by Vail & Vickers as a blacksmith shop, generator house, slaughterhouse, and cold storage that held a freezer for making ice. The building contains six rooms-a maintenance/repair shop once housing a blacksmithy, a former generator room equipped with two diesel generators, a workshop equipped with a saw and grinder, a butcher room with a loading dock out its door, and two walk-in freezers.

For more detailed historical information and citations, please refer to the Historic Resource Study: Island Legacies - A History of the Islands within Channel Islands National Park