Greater Merseyside is a term for the sub-region of North West England that includes Merseyside County and Halton. This corresponds, in part, to the original proposal for Merseyside and the River Mersey or Liverpool's hinterland. It has a semi-official usage by the local authorities of Merseyside County and Halton when they act together, co-ordinated through the Merseyside Policy Unit. Greater Mersyside is also one of the five sub-regions in the North West that are used by the Northwest Development Agency (NWDA).