The so called sanctuary cities are actually the main source of opposition to anti-immigrant federal policies in the United States. The central argument of this cross case study is that the category of sanctuary agglutinates a set of laws, policies and informal practices of different nature, with varied political genesis and different degrees of insurgency. This article argues that in-deep study of the context framing each different kind of sanctuary city helps to explain the existence of a contrasting spectrum. With the aims to contrast them, three representative categories within the spectrum are analyzed: sanctuary of rhetoric, informal sanctuary, and welcoming sanctuary. This research concludes that the most representative sanctuary practices —the most contestative and with the highest degree of scalability— are linked to the need of the city to defend funding access and to protect its political autonomy; but also, they are linked to the capacity of organized migrants to make alliances with local political stakeholders.