However, as early as 1894, mine production outstripped the capacity of the mill, and a new mill was planned.

The second stamp mill was built just north of the first; this mill was an iron-framed structure measuring 132 feet by 216 feet.
 It was constructed in 1899 by the Wisconsin Bridge and Iron Company at a cost of $22,450.
 The second mill opened in late 1900 with three mills.
 To service the additional capacity, new boiler and pump house buildings were also constructed.
 Over the next two decades, minor alterations were made to the structures of the complex (including the erection of a new 175-foot smokestack for the boilerhouse in 1916) while the milling process and machinery were continuously refined.

However, the rise in the price of copper during World War I provided both impetus and resources for expansion of the site.
 Reinforced concrete and brick additions to both stamp mills were constructed in 1919; the addition to mill no.
1 was 123 feet by 215 feet, and the addition to mill no.
2 was 91 feet by 132 feet.
 The additions were equipped and functioning by 1920.
 The mill also changed their production of electrical power, building a structure to house a new turbine near mill no.
1.
 Construction on the new building, a brick structure measuring 36 feet by 38 feet by 45 feet high, began in 1921; the turbine was online in 1923.
However, as early as 1894, mine production outstripped the capacity of the mill, and a new mill was planned.
The second stamp mill was built just north of the first; this mill was an iron-framed structure measuring 132 feet by 216 feet.  It was constructed in 1899 by the Wisconsin Bridge and Iron Company at a cost of $22,450.  The second mill opened in late 1900 with three mills.  To service the additional capacity, new boiler and pump house buildings were also constructed.  Over the next two decades, minor alterations were made to the structures of the complex (including the erection of a new 175-foot smokestack for the boilerhouse in 1916) while the milling process and machinery were continuously refined.
However, the rise in the price of copper during World War I provided both impetus and resources for expansion of the site.  Reinforced concrete and brick additions to both stamp mills were constructed in 1919; the addition to mill no. 1 was 123 feet by 215 feet, and the addition to mill no. 2 was 91 feet by 132 feet.  The additions were equipped and functioning by 1920.  The mill also changed their production of electrical power, building a structure to house a new turbine near mill no. 1.  Construction on the new building, a brick structure measuring 36 feet by 38 feet by 45 feet high, began in 1921; the turbine was online in 1923.
Quincy Mining Company Stamp Mills Historic District