Boswell owned a large library, comprising mostly antiquarian, topographical, and historical works. In anxiety about Napoleon's planned invasion of the United Kingdom, Boswell also produced a map of his home county in 1804, which was later lithographed for private circulation. This map was produced mostly with reference to the government and resources of the county, containing: "the site of the beacons, and their communications with each other – the signal-posts erected by the Government – the depôts and places of assembly of the volunteer corps – the number of the inhabitants of the county comprising the volunteers actually serving – the number of persons capable of bearing arms, guides, conductors, &amp;c. and a general summary of the resources of the county as to the live and dead stock, the services to be performed by individuals, supplies to be furnished, the number of mills and ovens, of boats and barges, &amp;c. the whole forming a most complete statistical account of the county in that year, compiled from the returns made under the Act for defence and security of the realm".