The Congress of Vienna in 1815 did not debate the future of Gibraltar at all, and therefore the retention by Britain of sovereignty over the peninsula was confirmed by default. A porous land frontier with Spain allowed overland migrants to join those arriving as before by sea, and they mixed with a civilian population that in any case was growing by natural increase. What was not increasing was the size of Gibraltar to accommodate them. What was not decreasing was the concern of Gibraltar's local and London managers about the composition of visitors and of the resident civilian population. Civilian experiences and, indeed, their sense of a common identity were therefore to be seriously affected by how, and how effectively, those in authority operated immigration controls. This chapter first examines population growth in Gibraltar from 1815 to 1901, before turning to the regulation of aliens, the response of civilians to the rules on aliens, and the Aliens Order-in-Council of 1873 and 1885.