The canal also continued in use and such was the traffic need that both the railway and the canal were in heavy use, with the canal company remaining highly profitable until the 1870s.
The TVR skirted the town to the east of the town wall with its station on the Spital, the land of the old hospital at the end of what was then Crokerton (Crockherbtown), now Queen Street, and the offices of the company were built adjoining the station in 1860. The company had its own locomotive works at the Docks and carriage building and repair shops at Cathays. An additional station was built alongside the Bute West Dock on land leased from the Bute Estate.
Between 1837 and 1841 the Great Western Railway (GWR) was constructed from London to Bristol (with Isambard Kingdom Brunel as engineer), and in 1845 the South Wales Railway, originally promoted at Swansea and Cardiff to run from Stonehouse, Gloucestershire via Chepstow, Newport, Cardiff and Swansea to Milford Haven in Pembrokeshire with the aim of linking by sea with Ireland, was incorporated. Again Isambard Kingdom Brunel was the engineer in charge. In 1850 the first train ran from Cardiff to Swansea. The line was quickly taken over by the GWR and linked with that system and by 1853 the link to Milford was made. There was, of course, at this time, no direct rail connection from Cardiff to Bristol, the railway running via Gloucester and Chepstow. Connection between Bristol and South Wales remained by boat via Portskewet, near Chepstow from where the railway could be used to travel to Newport, Cardiff etc.
A problem arose in connection with the siting of the station of the South Wales Railway in Cardiff. The company's intended site for the station, just outside the South Gate, presented serious engineering difficulties crossing the curve of the River Taff. Eventually agreement was reached for the straightening of the river by the building of a new channel, allowing the railway approach to the site of the station to be more easily accomplished. This considerable engineering undertaking was carried out between 1849 and 1853. The straightening of the river resulted in the "cutting off" of the part of the river where the old Quay had stood, which explains why Quay Street and the Golate, which figure prominently in the earlier part of this account are now nowhere near the river ! They lead from St.Mary Street to Westgate Street, the latter having been built over the site of the Quay, whilst the site of the old river course further South became known as Temperance Town when Jacob Matthews built a Temperance Hall there (later Wood Street Chapel).
During the period 1830 to 1850, then, the building of the West Bute Dock and the coming of the Taff Vale and South Wales Railways had transformed the old town, bringing it into the mainstream of industrialisation.