The fenlands, that stretch down as far as Norfolk, are former wetlands consisting both of peat bogs and tidal silt marshes which were virtually all drained by the end of the 19th century when Firsby had its longest period of growth. The former peat fens and silt marshes provided a rich loamy soil that was ideal for the growing of cereal and vegetable crops, and gave Lincolnshire its reputation as being the 'bread basket' of England. The resulting flat lands also made an ideal environment for the later mechanisation of farming in the mid-20th century. Firsby has always been an agriculturally based village with a dark and rich loamy soil over a heavy clay subsoil.