To date, there has been no attempt in Ontario economic history to examine human fertility in the nineteenth century by area of the province where area is differentiated by the extent of agricultural development and the data used are at the household level. In the United States, Richard Easterlin and his colleagues (1978) used a sample of rural households from the 1860 manuscript census to look at fertility, family, and agricultural differences and similarities for old and new areas in the northern states. The present study takes the census districts of Canada West (now Ontario) in 1851, divides them into three groups by the percentage of ever-improved agricultural land, and uses a sample of farm households from the manuscript census of 1851–52 as the data set. Since the extent of agricultural development can be taken as a proxy for county wide land availability, the contribution of this study is to relate land availability at both the county and household levels to fertility in the mid-nineteenth century.