Estate maps are a wonderful source for garden and landscape history, as they can show incredible detail. The Hertfordshire Gardens Trust has done a great deal of work based on the wonderful resources to be found in Hertforshire Archives and Local Studies. You can see the results of some of their research in publication The Parks and Gardens of West Hertfordshire.
Bills and Recipts
Roses from Thomas Rivers
Capability Brown
design for Youngsbury, Standon, 1770
Estate maps
Bayford Place, detail from Bayfordbury estate map, 1807