By the early 1960s, Clarke worked for the
United States Department of Defense in
Washington, D.C. in the office of the
Army Chief of Staff. He worked within the Pentagon, with nine separate top-level security clearances. His position had allowed him to spread pamphlets regarding gay rights during his time in the army. The access and influence from his position would aid the efforts of Jack Nichols and the
Mattachine Society, which Clarke had joined after the
Lavender Scare, to pressure government legislature concerned with
gay rights. Clarke and Nichols created new chapters of the
Mattachine Society by producing the East Coast Homophile Organization (ECHO). The Mattachine Society was the first
gay liberation organization in the United States. Clarke became a leader of the group's New York and Washington, DC chapters. Clarke helped to organize the first gay rights picket line outside of the
White House in 1965, he even hand lettered the protest signs himself. Some of which read "Gay is good!", which in the mid-1960s became a sort of rallying cry to combat both the guilt and shame heaped on gay people by the larger society. Clarke and Nichols created and wrote "The Homosexual Citizen" as a continuation to their original column written for
The Mattachine Review beginning around 1965. It was published in
Screw magazine. By 1972 they edited
Gay (which was affiliated with
Screw), Clarke and Nichols authored two books about same-sex attraction. ==
Gay newspaper ==