Museums have the capacity to enhance social cohesion, which is the product of a trusting, connected community. History museums and historic sites, in particular, can serve communities by stimulating dialogue on difficult issues, accurately representing all the people of a nation, and creating forums for discussion among groups with disparate opinions. History museums promote social cohesion by solidifying the identities of their audiences—as members of communities, ethnic groups, nations, and the world. This article combines extensive research with firsthand experience in history museums to accurately portray the ways different museums affect social cohesion. It looks first at what social cohesion is, and the ways in which both civil society and educational organizations contribute to it. It makes the argument that museums share attributes of both civil society and educational organizations. This article then addresses the different ways museums contribute to defining identity, bridging community divides, and addressing society’s most difficult issues. It does this with in-depth analysis of several Holocaust museums and the movement in Russia to memorialize sites of Stalinist terror.