This junction and box were on the Edinburgh and Dalkeith Railway's South Leith branch. The box opened with the development of the Lothian Lines (North British Railway).
Prior to opening this was a single track line, doubled around 1910. A siding burrowed under King's Road to reach the Westbank Brick and Tile Works which had a clay pit on the west side of Portobello's High Street.
The box opened north of Portobello Road, which was originally crossed by a level crossing.
To the north the original Edinburgh and Dalkeith Railway ran on the east, sea, side. On the west side was Meadows Yard, opened with the Lothian Lines. The two met at King's Road Junction and ran south together to Portobello (South Leith Junction).
The signal box was opened in 1915. Sidings with a travelling crane and rotary tippers were laid on the west side by a clay pit south of Portobello Road around 1920. The brick and tile works became the site of Portobello Power Station.
From 1966 the branch to Leith East (Leith New Lines (Caledonian Railway)) via Meadows Yard was controlled from the box.
The box closed in 1973 and line was singled. Portobello Power Box took over the signalling. With the building of Sir Harry Lauder Road it was realigned to the west, the site of the sidings with the crane, which has led to a rather right corner on the line where it passes under Portobello Road. The road now occupies the route of the Edinburgh and Dalkeith Railway.
To the south was Baileyfield Signal Box where the original line and a later NBR curve from Portobello enclose the Baileyfield Switch and Crossing Works.