Recently an unreported manuscript draft of a map of Lancashire from about 1604 by William Smith was located in the collections of the John Rylands Library in Manchester (Latin MS 509). In this note the new manuscript is compared with Smith’s printed map of Lancashire, for many years referred to as ‘Anonymous’, which was engraved from the 1604 manuscript, with the previously known 1598 manuscript map of Lancashire by Smith (Harley MS 6159) and with the four other known drafts for the Smith series in the British Library (Maps C. 2. cc. 2 [12‒15]). The comparison highlights Smith’s ability as a mapmaker and reveals some of the construction methods he employed. An underlying pencilled grid was used to transfer details from the 1598 draft and to convert from a cylindrical to a conic projection. Smith seems to be the first to have used such a projection for a county map, a novelty similar to his introduction of true north, and a key to map signs.