[1] A branch line to Cadia had been advocated for some years, with alternative routes from Spring Hill, Millthorpe or Carcoar being identified.

[2][3] After the blast furnace at Lithgow opened in May 1907, one reason for the iron ore deposit at 'Iron Duke' (Big Cadia) not being mined—although William Sandford had taken out a sub-lease to do so—was the absence of a rail connection and the poor state of the nearby roads.

[12] At the exchange sidings, there was an engine shed, capable of holding one locomotive, possibly later extended to be able to house two, and a water tank fed by a wind-driven pump.

[13][14][15] The line then ran just south of the road to Orange,[16] until just past the small village of Spring Terrace, where it continued westward.

[17] There were three private sidings between Spring Hill and Cadia;[18] 'Spring Terrace'—at a location to the west of the modern-day village, approximately 4 miles along the line—'Summit' approximately 5.5 miles along the line, and 'Cadia Road',[9][6][19][13] 'Summit' was described as a 'staging siding' and was at the bottom of a relative steep grade towards Spring Hill and before the beginning of the long decline to Cadia.

During this period, trains consisting of four-wheeled coal wagons—each holding 16 tons of iron ore—were hauled by a privately-owned 4-6-4 tank locomotive—also 'Iron Duke'—from Cadia to exchange sidings at Spring Hill.

[27] Iron ore mining at Cadia ended, around time of the relocation of blast furnace operations from Lithgow to Port Kembla in late 1928, and the branch line also closed.

[6] Cadia could not re-enter production immediately; the old aerial ropeway was beyond repair and a new, inclined, cable-hauled skipway and 15-miles of power lines had to be installed.

[33] Once mining of iron ore ceased around June 1945,[34] the rail line closed in August 1945 and the tracks were lifted.

[6][12] The formation of the old branch line is visible in places, including alongside the southern side of Forest Road near Spring Hill[16] and is discernible in aerial views over most of its route.