Using a boundary perspective (Alba and Nee 2003), I examine the marital behavior of three self-identified multiracial groups: black/whites, American Indian/whites, Asian/whites. With a focus on marriage with whites, I assess whether the boundaries of whiteness are expanding to include these part-white multiracial groups. Marrying whites at a large scale may signify that part-white multiracial Americans are in the process of being accepted as “white.” At the same time, due to differences in the racial identity experiences of multiracial groups, marital patterns may differ by racial combination. Based on analysis of 2008–2012 American Community Survey data, I find that the majority of all three groups are married to whites, suggesting that most members in these groups are on the path to whiteness. On the other hand, multinomial logistic regression analysis demonstrates that American Indian/whites and Asian/whites are more likely than black/whites to have a white spouse, relative to spouses of another race/ethnicity. Moreover, separate regression analyses by multiracial group reveal gender differences in their likelihood of marrying whites for black/whites and Asian/whites. These results indicate racial stratification in the marriage market among part-white multiracial Americans, with further stratification by gender for some groups.