[4] The line was extended to Mercer on 20 May 1875, though the pioneer British contractors, John Brogden & Sons, ran an excursion train the day before.

It described the route as crossing Mangatawhiri swamp, then running beside the South Road, with a short branch line being constructed to connect with the Waikato Steam Navigation Company's boats.

[11] The refreshment rooms gained importance when dining cars on main trunk expresses were removed as a wartime measure.

[83] A Wellington to Auckland "Limited" express derailed on 28 October 1940 killing the driver and fireman and injuring 12 passengers.

[88] Removal of the tunnel allowed double tracking and easing of the speed limit to 45 mph (72 km/h).

[91] In 2011 a feasibility report on reinstating passenger services said a station with a platform 155m long and 750mm high for 6-car trains would cost $4m.

[92] Today, the Te Huia Hamilton - Papakura services passes Mercer but does not stop.