Practitioners and policymakers often want estimates of the effect of an intervention for their local community, e.g., region, state, county. In the ideal, these multiple population average treatment effect (ATE) estimates will be considered in the design of a single randomized trial. Methods for sample selection for generalizing the sample ATE to date, however, focus only on the case of a single target population. In this paper, I provide a framework for sample selection in the multiple population case, including three compromise allocations. I situate the methods in an example and conclude with a discussion of the implications for the design of randomized evaluations more generally.