The Pittsburg & Buffalo Coal Company's Hazel Mine on the southeast side of Canonsburg was a high-volume coal operation. The mine's tipple was across the Chartiers creek from where the mine was. The mine entrance was under Buffalo Hill. The tipple was located in Canonsburg-proper, but the other side of the creek was part of the North Strabane township. The Hazel mine was a slope mine that reached coal about 80 feet below the water line at about 400 feet away. The chain haul had a capacity of 200 mine cars per hour (the mine had a complete rail yard underground). The main ventilating fan was 22 feet in diameter and 8 feet thick, housed in a concrete building for safety.
The mine was started in 1900, and reached coal October of that year, despite the fact that the power house, tipple, and railroad sidings were still being built. The Engineering and Mining Journal issue of that year describes the Hazel Mine in great detail. The formal opening was in July of 1901, with the local newspaper, Daily Notes calling it the "Greatest in the World" (yes, the media has been "reporting" fake news for more than 100 years). Records indicate that in 1902 it employed 450 men. In 1903, the book The Successful American describes the Hazel Mine in great detail. In that same year, the Pittsburg-Buffalo company was formed by the merger of several companies, including an existing company by the same name. By 1904 production had increased to the point where 100 railroad coal cars, each with a capacity of 30 tons, were being filled daily. To handle the cars, the company bought its own switching engine as noted in the local newspaper, Daily Notes, "Freight Locomotive for the Hazel Mines" in the September 29 issue.
In 1905 an additional shaft and power house were built on the property of the Greer farm to handle the excess slack. An extensive report dated 1910 shows that the mine was remodeled between 1903 and 1910 and was now producing 3,000 tons of coal per day. At that time, the tipple still covered just the original 4 tracks. The associated power house had 7 boilers totaling 1,200hp that used slack as their fuel source. It generated 150kW of electrical power. Its feedwater was softened and purified (presumably obtained from the creek, initially). There was a 7-foot blower fan to ventilate the mine. The report also states that there was a supply house and a railcar shop on the property to make repairs. The publishing house, Arcadia, has a book titled Canonsburg which contains a 1912 photo on page 49 of a flooded Hazel Mine.
Pittsburg & Buffalo Company purchases its own hopper cars in 1907. In 1915 a bank bought the Pittsburg & Buffalo Company assets as there were no bids during its bankruptcy auction. This led to the Hazel mine being closed. However, in 1916, the Chartiers Creek Coal Company was formed, which re-opens the mine. The Hazel mine opens full-time in 1917 to support WWI's efforts. In 1922 the Hazel mine strike lasts 6 months.
The tipple, now referred to as the Buffalo mine, burns down in 1929. Its stable and lamp house were lost earlier in the year. This causes the Chartiers Creek Coal Company to go into receivership. While the mine re-opens, in 1931 fire in the shaft of the mine closed it temporarily. In 1933 Standard Tin Plate buys Chartiers Creek Coal Company's assets. Canonsburg Coal Company was formed to rebuild and operate the Buffalo mine. Coal mines were unionized again; Buffalo Hill mine housing was demolished. The mine and tipple were rebuilt again in 1934.