They waited patiently to get their blood drawn, a crowd of young and middle-aged Queens residents in Corona Square. Two city nurses stood under the plastic tent and pricked the index finger of each outstretched hand, and one by one, extracted a small sample of blood.

Franklin Munoz, a priest...

Omar Ulffe, a 37-year-old immigrant from Peru, approached the pulpit at St. Leon's Catholic church in mid-Mass - something he does every week, at different churches, he said - and told the congregation about the importance of next year's national census. Ulffe has been canvassing Hispanic populations in neighborhoods like...