Runcorn is an industrial town and cargo port in the Borough of Halton, Cheshire, England. Its population in 2021 was 62,100. Runcorn is on …Runcorn is an industrial town and cargo port in the Borough of Halton, Cheshire, England. Its population in 2021 was 62,100. Runcorn is on the southern bank of the River Mersey, where the estuary narrows to form the Runcorn Gap. It lies on the southern shore of the River Mersey 15 miles upstream from the port of Liverpool.