The growth of Queer Sociology has produced a body of research focused on LGBTQ identity formation, while less has been discovered about subsets of this community, including later-life lesbians who were previously partnered in long-term heterosexual relationships with cisgender men. Several theories, including the Cass Theory of Sexual Orientation Identity Formation and Fassinger's Theory, provide a model which LGBTQ people may progress through as they develop their sexual orientation identity. These models provide insight towards the development of a lesbian identification later in life. Through sixteen in-depth interviews with lesbians in the United States who did not identify as lesbian until after age thirty-five, I examine the social barriers that impact these women's identity formation processes, and examine how sexual orientation identity development theories help us understand this process. My findings reveal that heteronormativity, compulsory heterosexuality, lack of representation, gendered expectations, and the pursuit of success all acted as societal barriers that delayed these women in their sexual orientation identity development. Thus, we see that Cass' recognition of the importance of the sociocultural environment is vital. However, the theory's commitment to linearity is still questionable, and her theory may not provide enough flexibility for the fluidity of sexual orientation. Alternatively, Fassinger's theory provides more space for sexual orientation to exist as a process of continuous development. / Master of Science / The field of Sociology expanded to research LGBTQ experiences and identities in the 1980's and 90's, forming the study of Queer Sociology. Since this formation, smaller subsets of the community have yet to be explored. This includes women who came to a lesbian identification later in life (after the age of thirty-five) who were previously partnered in long-term heterosexual relationships with cisgender men. These women are known as later life lesbians. Within the field of Queer Sociology, several theories have been developed to provide a process which LGBTQ people may progress through as they develop their sexual orientation identity. This includes the Cass Theory of Sexual Orientation Identity Formation and Fassinger's Theory. These models can be used to provide insight into the sexual orientation identity development of later life lesbians. Through sixteen interviews with later life lesbians, I examine the social factors that impact these women's sexual identity formation processes, and examine how sexual orientation identity development theories help us understand this process. My findings reveal that the societal expectation of heterosexuality, lack of queer representation, gendered expectations, and the pursuit of success all acted as societal barriers that delayed these women in their sexual orientation identity development. Based on these social factors, we see that Cass' recognition of the importance of the social and cultural environment is vital. However, Cass also commits to a linear development of sexual orientation identity, which remains questionable. Additionally, her theory may not provide enough flexibility for the fluidity of sexual orientation. Alternatively, Fassinger's theory provides more space for sexual orientation to exist as a process of continuous development.