Parishes and Extra-Parochial Places
The main organizational unit behind the London Bills of Mortality is the parish: a religious administrative unit usually consisting of one or more churches, their associated staff, and all Christians living within the geographical bounds of the parish. The parish clergy christened, married, and buried their parishioners and—starting in the sixteenth century—the parish clerk kept a register of those events. The burial numbers would eventually form the basis of the bills, with christenings added later.