In 1990, the Native American/First Nations gay and lesbian conference chose Two-Spirit as a better English umbrella term for some gender identities unique to Native American cultures, many of which can be considered as outside of the Western gender binary.[1]
The 1990 Bisexual Manifesto published in bi zine "Anything That Moves" shows explicit support of nonbinary gender by stating "Do not assume that bisexuality is binary or duogamous in nature: that we have 'two' sides or that we must be involved simultaneously with both genders to be fulfilled human beings. In fact, don’t assume that there are only two genders."[2]
The term "Gender Queer" was defined in a 1990 book titled The Welcoming Congregation Handbook as "A person whose understanding of her/hir/his gender identification transcends society's polarized gender system"[3]; it can be surmised that the term "gender queer" was likely in use even before this publication recorded it.