The census 1851-1911 provides a resource of information on employers and small firms that allows 200,000 – 2m individual entrepreneurs per year to be identified and the population of businesses to be estimated. This information has not been previous systematically available or researched. This paper outlines how information can be extracted from the population census, the way in which gaps and truncations in the I-CeM electronic records of the census of businesses can be overcome, and how the data can be enriched. The paper outlines how entrepreneurship is defined from the census and other records, how entrepreneurship rates can be calculated, and how database has been created that is as complete and consistent as possible to be deposited at UKDA.