Linked from
The 32 pages that link to Census, each with the reason it gives.
GenealogyRelated: Census entries can place relatives together in households at particular times.
Population growthRelated: Censuses provide the baseline counts used to estimate change over time.
Modal shareRelated: Census commute data are a common source for local passenger-mode estimates.
RedistrictingRelated: Census population totals provide the data used to adjust district populations.