<p>The term “county lines” describes gang members or Drug Trafficking Groups mobilization from large urban centers to expand their drug businesses into smaller communities. Research on county lines is mainly situated in the United Kingdom (UK) and primarily focuses on the exploitation of children and youth in these processes. However, how county lines manifest outside of the UK, and more critically, how these drug operations affect other vulnerable groups, such as low-income and unhoused community members in ‘receiver’ cities, remains ill-understood. This paper extends the empirical base by examining county lines drug operations in Thunder Bay, a mid-sized city in Ontario, Canada. Our paper illuminates how county lines contribute to the exploitation of marginalized persons and the cycle of homelessness. We coin the term “street colonization” to refer to how out-of-town Drug Trafficking Groups’ operations change receiver cities’ drug and street scenes and shape marginalized people’s perceptions and experiences of violence, fear, and precarity.</p>