This paper reports the first data on historical population structure in white Australians. Vital records and census data from two Tasmanian registration districts, Oatlands and Bothwell, were examined using surname analysis to investigate population structure in the nineteenth century. Both were colonising populations and therefore initially had massive immigration and a very high sex ratio. Inbreeding, as measured by marital isonymy, was relatively high in Oatlands, especially in the context of its short history. Although genetic continuity, measured by surname constancy, was relatively low, a small but distinct core was detectable. Bothwell, the smaller community, exhibited very little inbreeding and, concomitantly, low surname constancy. The coefficient of relationship by isonymy between Oatlands and Bothwell was extremely low. These findings are discussed in the context of the known socio-political history of this region of Tasmania.