Abstract
Like the European immigrants who streamed into American cities at the start of the twentieth century, the immigration researchers who first studied them took their upward mobility for granted and focused on their assimilation. As a result, the published research virtually equated assimilation with mobility. Nonetheless, assimilation and mobility were and still are independent processes; immigrants can assimilate without being mobile and vice versa. Consequently, I ask, whether, when and how assimilation causes or leads to mobility; but also whether mobility causes or leads to assimilation. The article considers some empirical and conceptual questions that emerge when the two concepts are separated.