[James Allen] didn't meet true injustice until the late 1970s, when he saw his first postcard of a lynching. The victim was a true celebrity. The 1913 trial of Leo Frank, a Jew, for murdering Mary Phagan, a young Christian, was every bit as notorious as those for Sacco & Vanzetti and the Rosenbergs. It spurred a furious debate over everything from religion to geography. It prompted the formation of the Anti-Defamation League. And it strengthened the Ku Klux Klan.

This epiphany made Allen a serious collector of lynching images. He became a sort of scholar, to show the wide range of mob murder with a message. He acquired pictures not only of black victims, but whites and foreigners. He acquired pictures not only taken in the South, the citadel of lynching, but Duluth, Minn., San Jose, Calif., and other supposedly more lawful places. He acquired not only postcards, but postcards inscribed viciously. He acquired not only lynching materials, but anti-lynching materials.

Allen said he's had more than 100 requests to exhibit the lynching documents. Yet directors of major museums refuse to display them, fearing a loss of support. "Their No. 1 goal," insisted Allen, "is self-survival."