The Mersey Railway tunnel connected Liverpool and the Wirral under the River Mersey, It opened in 1886, it is the second railway tunnel in the world to be built under water, the first tunnel in the world was the 1843 Thames Tunnel in London that origally was a pedestrian tunnel but was converted to a railway tunnel in 1869.

 

The Mersey Tunnel was constructed by John Waddell, who had been sub-contracted the work by Samuel Isaac, it was designed by Sir Charles Fox, and the design was carried out by his son, Douglas Fox. Douglas Fox was later knighted for his work on the project after its official opening by the Prince of Wales, later King Edward VII.

 

In December 1879, tunnelling work started. The initial tunnelling failed with work recommencing in 1880. Three tunnels were built. The main twin track rail tunnel is 26 foot wide and 19 foot high. The tunnel lining was 6 to 8 layers of brick. The other two smaller tunnels were for drainage and ventilation. After initially using explosives and hand tools, in 1883 a new boring machine, the compressed air driven Beaumont Cutter, was introduced. Progress improved rapidly. Telephone lines were laid through the tunnel between Liverpool and Birkenhead improving communications.

 

The Mersey Railway opened between Green Lane station in Birkenhead and James Street station in Liverpool in 1886, via Birkenhead Central and Hamilton Square stations, both in Birkenhead.

In 1888 a branch to Birkenhead Park station opened, with a connection to the Wirral Railway.

This was followed in 1891 by an extension from Green Lane to Rock Ferry with a connection to the Birkenhead Railway.

The whole of the ventilating system was supplied by Walker Brothers, comprising five fans with the steam engines for driving them. Four were Walker's improved Guibal type, and one was the Walker 'Indestructible' type, erected near Liverpool Central Station.

In 1892 the tunnel was extended from James Street to a new Low Level station at Liverpool Central. The total length of the tunnel was 3.12 miles and by 1890 it was carrying 10 million passengers a year. By 1975 the section of tunnel from James Street to Liverpool Central was no longer used by passangers but is still used as the only way for wirral line trains to connect with the northen lines.

 

Because of smoke from the steam engines making breathing difficult in the tunnels and underground stations, the tracks in the tunnel were electrified in 1903 initially using 4th rail converting later to 3rd rail becoming the first underground railway in the world to change over completely from steam to electric power. It was originally electrified with a fourth rail system, which was later replaced by a third rail system. The nearby Liverpool Overhead Railway, the world's first electric overhead railway, had already operated successfully with electric traction since its opening in 1893.

 

The Mersey Railway electric trains ran from Liverpool Central to Birkenhead Park and to Rock Ferry, where passengers to points beyond would change. In 1938 the LMS electrified from Birkenhead Park to New Brighton and to West Kirby, and built new trains which ran through to Liverpool. Normally new LMS trains handled the West Kirby route and Mersey Railway trains handled the New Brighton service, as well as the existing Rock Ferry operation. In 1948, on nationalisation of the railways, the Mersey Railway became known as the London Midland Region Mersey section.

 

In 1886, a tunnel was planned to branch from the under-river tunnel from the river side of James Street Station to Huskisson Dock. This would carry mainly freight from the Wirral side of the river. The full tunnel was never built, however the branch tunnel headers were built to a very short length. This was later used for the new Merseyrail Wirral Line Loop tunnel through Liverpool city centre in the 1970s.

 

The tunnel and railway are still in use today as part of the Wirral Line of the Merseyrail network.