The idea that the Rivers Mersey and Irwell should be made navigable from the Mersey Estuary in the west to Manchester in the east was first proposed in 1660, and revived in 1712 by Thomas Steers. In 1720 the necessary bills were tabled. The Act of Parliament for the navigation was received in 1721. The construction work was undertaken by the Mersey & Irwell Navigation Company. Work began in 1724, and by 1734 boats "of moderate size" could make the journey from quays in Water Street, Manchester,Coordinates: to the Irish Sea. The navigation was suitable only for small ships, and during periods of drought, or when strong easterly winds held back the tide in the estuary, there was not always sufficient draft for a fully laden boat.
Eight weirs were constructed along the length of the route, and some short cuts were made around shallower parts of the river, with locks, to enable the passage of boats. Some difficult turns along the river were also removed.
The navigation was modified and improved on a number of occasions. A canal section known as the Runcorn and Latchford Canal was added in 1804, to bypass part of the lower reaches. In 1740 the company built quays and warehouses along Water Street in Manchester.
In 1779 a group of businessmen from Manchester and Liverpool purchased the navigation, and began making improvements. A difficult section below Howley lock was cut out by the building of the Runcorn to Latchford Canal, and at Runcorn a basin was built for boats to wait for the tide.
An aqueduct was built from Woolston Cut, to replace water lost from the locks that were used to raise boats into the new canal section.