Between 1792 and 1992 promoters of canals, railways and other public works had to deposit large-scale plans showing the route of the proposed undertaking, and also a schedule of all the land to be taken, with the clerk of the peace of every county and large borough through which the route was to pass. These `deposited plans', as they are known, were retained whether or not the project went ahead and are now kept in county record offices. Although well known to canal and railway historians, deposited plans have not been as widely used as some map sources because only a few detailed catalogues have been published. This guide describes nearly 400 sets of documents and lists all the parishes (not merely those in Northamptonshire) through which each scheme was to pass. These include several unexecuted projects for canals between London and the Midlands, as well as numerous lines promoted by the London & North Western Railway in the west of the county, by the Great Northern and Great Eastern in the east, and by the ill-fated independent companies which tried to build an east-west route through south Northamptonshire.