The Mahanoy City Colliery was located just north of the Mahanoy City borough line. The opening was a drift driven west on the south dip top split mammoth vein by Hill and Harris in 1860. In 1862, they drove the water level mud tunnel to the mammoth vein and their first shipment was 12,240 tons of coal. Hill and Harris continued developing the colliery by sinking the slope 366 ft. on the top split mammoth vein and drove a tunnel south to the primrose vein in 1870. The same year they erected a large double breaker with a screen capacity to prepare 600 tons of coal daily and it was considered the finest equipped colliery in the anthracite region.
In 1870, Rommel was admitted in the firm to form a new company of Rommel, Hill & Harris, who operated the colliery until 1873 when it was purchased by the Philadelphia & Reading Coal & Iron Co. They sank a pump slope east of the hoisting slope and extended the mine workings to other veins of coal by tunnels and increased the shipments from 54,414 tons in 1869 to 127,006 tons in 1874.
In 1899, the hoisting slope was extended to the third level and the coal hoisted in gun boats.
In 1903, an inside shaft was sunk to the basin of the buck mountain vein.
In 1911, an electric haulage system was installed in the water level, third level and underground shaft workings and in 1914, an inside slope was sunk 651 ft. across the pitch of the primrose vein.
In 1916, the no.5 inside buck mountain slope was sunk below the eighth level in the schuylkill section of the colliery.
The colliery breaker was razed in 1936 and the Mahanoy City Colliery consolidated with the Knickerbocker Colliery in 1951. All mining ceased on Mar.15,1953.
The total shipments of coal to 1928 from the Mahanoy City Colliery was 10,959,662 tons.