On February 26, 2012, 17-year-old Trayvon Martin was shot and killed by George Zimmerman in Sanford, Florida, because as a Black boy walking in a gated community, he was deemed “suspicious.” Zimmerman’s acquittal appalled a nation often willfully blind to the vulnerability of living while Black. Ten years later, “Black Lives Matter” has grown from a hashtag to a protester’s cry to a cultural force that has reshaped American politics, society, and daily life. It is, at the same time, a specific collection of organizations and people whose decisions have attracted both applause and criticism; whose actions have been a source of intrigue; whose personal relationships have both strengthened and splintered under the stress and exposure. This special issue attempts to tell the story of the first decade of Black Lives Matter, the movement — as well as the country it moved