Hagerman was approached by the owners of the Buena Vista mine, who were convinced that properties adjacent to their claim also contained gold.
Following the pattern established in Aspen, Hagerman and his partners purchased 22 adjoining properties and formed the Isabella Gold Mining Company.
The mine became a major success.

Hagerman was one of three mine owners to precipitate the Cripple Creek miners' strike of 1894.
The mine owners, who employed about a third of the miners in the area, extended the work-day to 10 hours while refusing to increase pay.
The workers, represented by the Western Federation of Miners, struck.
Although some smaller mining companies capitulated immediately, the remaining owners (including Hagerman) raised a paramilitary force under the legal protection of the local sheriff.
 After a tense and somewhat violent standoff, the governor sent in the state militia to protect the miners.
Hagerman and the other mine owners agreed to return to the eight-hour day.
It was a major victory for the union.

In 1898, Hagerman sold his stake in the Isabella Gold Mining Company and turned his remaining Colorado interests over to his son, Percy.
Hagerman was approached by the owners of the Buena Vista mine, who were convinced that properties adjacent to their claim also contained gold. Following the pattern established in Aspen, Hagerman and his partners purchased 22 adjoining properties and formed the Isabella Gold Mining Company. The mine became a major success.
Hagerman was one of three mine owners to precipitate the Cripple Creek miners' strike of 1894. The mine owners, who employed about a third of the miners in the area, extended the work-day to 10 hours while refusing to increase pay. The workers, represented by the Western Federation of Miners, struck. Although some smaller mining companies capitulated immediately, the remaining owners (including Hagerman) raised a paramilitary force under the legal protection of the local sheriff.  After a tense and somewhat violent standoff, the governor sent in the state militia to protect the miners. Hagerman and the other mine owners agreed to return to the eight-hour day. It was a major victory for the union.
In 1898, Hagerman sold his stake in the Isabella Gold Mining Company and turned his remaining Colorado interests over to his son, Percy.
J. J. Hagerman