The section of line on which Ponkey Crossing Halt was located part of the 1¾-mile Great Western Railway (GWR) Ponkey Branch. The GWR opened the Ponkey Branch railway between Gardden Lodge Junction (on the Shrewsbury and Chester line), furnaces at Ponkey and Aberderfyn and Bryn-yr-Owen Colliery on 1 August 1868; the line was single track.  On 27 August 1876 it was extended beyond Bryn-yr-Owen to the short-lived Legacy Colliery – which had ceased operation in 1875. The OS 25-inch map of 1900, published 25 years after the colliery closed, refers to it as the Legacy Colliery Branch. The 6-inch scale OS map for the area published in 1879 showed connections to Gardden Pit, Brandie Pit and Park Pit at the southern end of the line. Just north of the level crossing after which the halt would take its name there was a connection to the Ponkey Brick and Tile Works.

By the time of the publication of the 1900 6-inch scale map a large gasworks had been established on the north side of the level crossing on the west side of the line; Johnstown Village had also expanded considerably.

In 1901 the GWR opened its Rhos branch which passed through Legacy and a connection was made with the Ponkey Branch.

Passenger services were introduced onto the Rhos branch on 1 October 1901 and enhanced through the introduction of a rail-motor service on 1 May 1905. In 1906 a signal box opened at Ponkey Crossing; it was provided so that a rail-motor passenger service could also be introduced onto the Ponkey Branch. The signal box had a 7-lever frame but that is all that is known about it. The upgrading of the section of line between Ponkey Crossing and Legacy for passenger services seems to have coincided with that section of the line being referred to as the Legacy Branch (‘Colliery’ having been dropped from the name).

Ponkey Crossing Halt was opened on 5 June 1905. To date no photographs of the halt have appeared so it is not known what facilities it possessed. The OS 25-inch map of 1909 names Ponkey Crossing Halt and shows a short platform east of the single track; the platform was probably constructed of timber. What is most likely a waiting shelter is about midway along the platform. There is no firm evidence of the 1906 signal box on the map. Signal posts are shown, which is to be expected on a line that had passenger services.

The steam rail-motor service ran between Ponkey Crossing Halt and Wrexham General. The GWR was not averse to providing unstaffed halts as branch termini, as seen also for example at Wynn Hall (terminus of the extended Rhos branch), Moss (north of Wrexham), Old Ynysybwl  (Glamorgan) and Drybrook (Glos). Unusually, all three of the stopping places on the Ponkey Crossing branch were halts and they were extremely closely spaced: Ponkey Crossing and Aberderfyn were 14 chains apart, and 15 chains separated Aberderfyn and Fennant Road. Rail-motors called at these halts and at Legacy and Rhostyllen stations. The journey overall journey time between Ponkey Crossing Halt and Wrexham General was 17 minutes which was relatively fast. However, Ponkey Crossing Halt had competition for Wrexham journeys in the form of the Wrexham and District Electric Tramways which had opened an electric tramway between Johnstown and Wrexham on 4 April 1903. The electric car sheds were adjacent to Ponkey Crossing Halt on the east side of the line. Although the trams were slower than the trains they took passengers into the town centre; Wrexham General station was inconveniently located half a mile from the centre.

Despite tramway competition the November 1906 timetable (click here) showed a generous service of twelve trains in each direction on Monday-to-Friday with three additional services on Saturday. Within a few years, however, the GWR had clearly tired of trying to compete with the trams as the company withdrew the rail-motor service on 22 March 1915 and, with almost indecent haste, track-lifting south of Legacy began two years later. Ponkey Crossing signal box was closed in 1929 and by the 1930s the line had been cut back to a point half a mile north of Ponkey Crossing. The 6-inch scale map of 1938 refers to the branch by its original name (Ponkey Branch).

The Ponkey Branch passed into British Railways ownership in January 1948 and remained in use to serve the Ponkey Gasworks until 31 August 1964.

The electric tramway closed on 31 March 1927.