After the 2 nd World War, traffic on the canal began to decline despite the use of the fleet of motor lorries, which the Canal Company had built up at various places throughout the country. In 1950, the company was nationalised and became part of C.I.E.

Athy, with its ideal location, being situated on two major watercourses is in a unique position to attract both industrialists and sports enthusiasts. The development of both the Barrow and the canal could make Athy a most important midland town.

The River Barrow rises in the Slieve Bloom Mountain Range between the villages of Clonaslee and Rosenaller. Its primary directional flow is in a northeasterly direction, however on reaching the Laois/Offaly border; it changes direction turning to the southeast passing within one mile of the town of Mountmellick. From here on the course is predominantly eastwards, the river finally reaching Portarlington some seven miles further upstream. Just under a mile from Monasterevin, the Barrow is joined by the Eigile River. The Eigile together with its tributary rise in the Bog of Allen within a few miles of Daingean passing the village of Clonbullogue along the way. At Monasterevin, the Barrow is crossed by the aqueduct carrying the Grand Canal on it's way to Athy, and it is on reaching Athy that the junction between the canal and river navigations take place. 

By far, the most important work of inland navigation carried out in centuries past, is a still water navigation, extending from Dublin across the country to join the Shannon near the town of Banagher, with a branch running south joining the River Barrow at Athy. The branch was formerly used for navigation but now only for water supply. It is approximately eight miles long as it is terminated near the Curragh of Kildare, to the south of the Grand Canal. Just beyond the 19 th lock at Lowtown, the Barrow line to Athy branches off to the south, and the main line swings in a more northwesterly direction and enters the Bog of Allen.

Returning to Lowtown, the junction with the Barrow line now occurs beyond the 19 th lock as stated above. The distance from Lowtown to Athy is 28 miles, upon which are some nine falling locks, two of them with double chambers. Seven miles beyond Vicarstown is the 26 th lock at Cardington Bridge, and another mile brings the canal to Athy. Here, there are two locks, the second effecting the canal with the River Barrow. The junction with Monasterevin was reached in 1786 while it was five years later that the junction with Athy was effected in 1791. It was considered that the new branch should go off at Monasterevin after the construction of an aqueduct over the Barrow to carry the line to Athy.