The Chicago occurrence is located on a ridge separating La France and Baker creeks, approximately 10.5 kilometres north east of the La France creek mouth on Kootenay Lake. The adits exposed over elevations of 2240 to 2350 metres.
The area is predominantly underlain by a north trending sequence of argillite and quartzite units of the Middle Proterozoic Mount Nelson Formation (Purcell Supergroup). This assemblage abuts the older conglomerate unit of the Upper Proterozoic Toby Formation (Windermere Supergroup) to the west and sedimentary rocks of the Dutch Creek Formation (Purcell Supergroup) to the east.
Locally, laminated and massive dolomites and siliceous limestones host sphalerite, galena and minor tetrahedrite mineralization. The sulphide mineralization occurs as networks of veins, stringers and irregular pods with silica-carbonate alteration.
In 1976, underground sampling yielded up to 0.33 per cent lead, 2.82 per cent zinc, and 4206.6 grams per tonne silver from a grab sample (508) of a oxidized fracture zone near the end of the 2350 level adit, while a 2.0-metre chip sample (502) of similar material, from the 2350-1 cross-cut, assayed 2.22 per cent lead, 2.75 per cent zinc, and 32.5 grams per tonne silver (Assessment Report 6109). Sampling of the 2240 level adit, near the 2240-6 cross cut, yielded up to 31.50 per cent lead, 0.19 per cent zinc and 1727.1 grams per tonne silver from a grab sample (634), while a 2.0-metre chip sample (643) from the same area assayed 5.07 per cent lead, 3.5 per cent zinc and 221.6 grams per tonne silver (Assessment Report 6109).
In 1990, a rock sample (RV9018) assayed 116 grams per tonne silver, 0.643 per cent copper, 0.366 per cent zinc and 0.276 per cent lead (Assessment Report 20708).
During the 1890’s and early 1900‘s, three adits, referred to as the 2240, 2310 and 2350 level adits, were developed on the Montana (L.7230) Crown grant and one adit, referred to as the “Sink Hole”, was constructed on the Celebration (L.7229) Crown grant. A total of 630 metres of underground development in cross-cuts and drifts are reported. No production figures have been reported for the workings.
In 1972, Bullis Engineering completed a program of geological mapping, and rock, silt and soil sampling was completed on the area as the Peg group. In 1976, Serem Limited completed a program of underground chip and soil sampling, geological mapping and a 6.0 line-kilometre ground electromagnetic survey on the area as the Wall claims. In 1979, Dekalb Mining completed eight diamond drill holes, totalling 704.4 metres, on the Celebration Crown grant. In 1990, Cominco completed a program of geological mapping and rock, soil and previous drill core sampling on the area. In 1995, Hunter Resources completed a program of prospecting and minor trenching on the area.