I am particularly pleased to see this paper in print, it took fifteen years and the help of over 50 research assistants to collect the data for this study. This paper started as a pet project the year my wife and I moved to Boston. That year, there was an article in the Boston Globe about a woman in Montreal who was attacked on a street and left unaided by passerbys. The Globe suggested that despite Canadians reputations, maybe Americans were now more altruistic. A hypothesis ripe for testing! Replicating an approach often associated with the famed social psychologist Stanley Milgram, with much assistance, I set out to “lose” nearly 4,000 letters in 62 urban areas in the US and Canada. The return rate served as a measure of helping/altruistic behavior. In 2001, the data confirmed a statistical tie. But, the end of data collection in 2001 also marked the horrible events of 9/11. It was immediately clear that this was an opportunity to measure how one of the most tragic events in American history might change community helping behavior. I sat on the data for ten years, returning to the field in 2011 and replicating the study in the same 63 urban areas. I expected to find a spike in helping behavior in the United States. Surprisingly, there had been a 10% decline in altruistic behavior in the United States relative to Canada. And, the decline was especially strong in those communities where the proportion of non-citizens had increased. Even more surprisingly, the trend was in the opposite direction in Canada. Since 2001, areas of Canada where the proportion of non-citizens increased experienced an increase in altruistic/helping behavior. What changed over that decade? One of the most obvious is the divergence in Canadian and US attitudes and policy towards immigrants. Canadian public opinion and the political rhetoric towards immigrants and diversity in general is much more positive than in the US. While Canada has institutionalize policies aimed at inclusion, valuing diversity, and a relatively speedy path towards citizenship, the US has not. Unintended evidence of how intolerance can hurt us all, while policies of inclusion and respect for diversity can lift us up. I discuss the implications of this trend a little further in an op-ed on why we should Stop blaming Facebook for Trump’s election win that was published in The Hill.