The Sankey Canal lies in the County of Lancashire and the Act of Parliament that sanctioned its construction received the Royal Assent in 1755 during the reign of George II. Its purpose was principally to carry coal for use in the growing chemical industry that was springing up in the Mersey Basin. By 1757 it was carrying coal and this made it the first canal to be constructed in England at the outset of the Industrial Revolution. Its opening accelerated expansion of the chemical industry and this developed along the line of the canal from Widnes, through Newton-le-Willows and Earlestown and then on to St Helens. Up to the time that the canal opened these towns were just small villages.

The mainline of the canal began at Blackbrook, close to St Helens, and it proceeded by Earlestown, Winwick, Sankey Bridges and Fiddler's Ferry, where there was an entrance to the river Mersey. Later, it was extended alongside the northern bank of the river Mersey to Widnes, where it terminated at a second entrance to the river Mersey at a place known as Spike Island.

The canal had three short branches around St Helens (marked A,B & C in the following list and on the map). The Boardmans Bridge Branch had one branch, the Ravenhead Branch.

1. Blackbrook Branch
2. Gerrards Bridge Branch. From Blackbrook to near Gerrards Bridge on the northern side of St Helens
3. Boardmans Bridge Branch at St Helens, terminating on the southern side of St Helens
4. Ravenhead Branch
5. The unconnected Ravenhead Canal

The unconnected Ravenhead Canal was about 600 yards long near Thatto Heath. The two names, Ravenhead Branch and Ravenhead Canal both took their name from the Ravenhead district of St Helens. Situated at Ravenhead was Ravenhead Colliery, Ravenhead Glass Bottle Works (Nuttall and Co), Ravenhead Glass Plate Works (British Glass Plate Co) and the Ravenhead Copper Works (Ravenhead Copper Co).

The glass industries in the Ravenhead area of St Helens eventually developed as the St Helens Crown Glass Co at the St Helens Crown Glass Works.

Statistics of the Sankey Canal
The type of boat using the Sankey Canal and its branches was the Mersey Flat and there was a towpath throughout.

The Sankey Canal was designed so that Mersey Flats could use it because these were the type of sailing boat then in use along the rivers Mersey, Irwell and Weaver, as well as along the coats of Lancashire and North Wales. As some of these boats were fitted with masts, roads that crossed the canal had to cross on swing bridges. Following the dawn of the railway era, with the opening of the Liverpool and Manchester Railway in September 1830, railways were also required to cross it on moveable bridges but an exception to this was George Stephenson's magnificent Sankey Viaduct at Earlestown, which crossed high above the canal.

Typically, a Mersey Flat had a length of between 68 feet and 72 feet 6 inches with a beam of between 14 feet 3 inches and 15 feet 9 inches and they could carry up to about 80 tons of cargo. These dimensions also gave some of them access to the Mersey & Irwell Navigation, the Bridgewater Canal and the northern section of the Shropshire Union Canal. It is understood that only two Mersey Flats have survived, Mossdale and Oakdale.

The first staircase locks to be built in England were the double locks at Broad Oak, St Helens, which came to be known as the Old Double Lock. Later on, another arrangement of double staircase locks was built on the Boardmans Bridge Branch at its junction with Gerrards Bridge Branch at Parr and these came to be known as the New Double Lock. Staircase locks are so arranged that the top gate of each lock, except the top lock, also form the bottom gate of the lock above.

Following its opening for trade, the Sankey Canal was an immediate commercial success and its opening was soon followed by that of the nearby Bridgewater Canal on the 17 July 1761. The opening of the Bridgewater Canal ushered in the era of Canal Mania, which was at its widest extent between 1789 and 1796. Subsequently, canal links for the Sankey Canal were considered but they came to nothing. These were:

A link to the Leeds and Liverpool Canal at Leigh. A link to the Bridgewater Canal and to the Trent and Mersey Canal by means of an aqueduct over the river Mersey at Runcorn.

To begin with, two short extensions of the canal were cut. In 1762, the canal was extended from Sankey Bridges to Fiddler's Ferry, to improve locking down to the river Mersey, and in 1775 it was extended into St Helens. The final extension, known as the 'New Cut, was the longest and this occurred in 1832 when it was extended alongside the northern bank of the Mersey to Spike Island, Widnes, where two locks were built, side-by-side. These were larger than the other locks on the canal. The construction of this extension was brought about in an attempt to counter competition from railways. A small dock, Widnes Dock, was also built immediately to the east of the two locks and this was provided with a separate lock.

The Sankey Canal was taken over by the St Helens Railway Company, to form the St Helens Canal and Railway Company, and after 1845 it generally became known as the St Helens Canal. Afterwards it was owned by the London and North Western Railway, which became an integral part of the London, Midland and Scottish Railway at the time of the railway grouping on the 1 January 1923.

Although the canal was principally built to carry coal down its length, the last bulk traffic to be carried on it was in the opposite direction. This was raw sugar from Liverpool, which was carried to the Sankey Sugar Works at Earlestown. This sugar trade ceased in 1959 and this led to the closure of the last navigable section in 1963. The canal above the sugar works was abandoned in 1931 and soon afterwards fixed bridges replaced the swing bridges. In spite of these changes, the abandoned section of the canal remained, more or less, in water, right into St Helens but a length of this was lost in 1898 when Canal St was built over it.