Initially ephemeral, many "vici" were transitory sites that followed a mobile unit; once a permanent garrison was established they grew into larger townships. Often the number of official civitates and coloniæ were not enough to settle everyone who wished to live in a town and so "vici" also attracted a wider range of residents, with some becoming chartered towns where no other existed nearby. Some, such as that at Vercovicium (Housesteads), outgrew their forts altogether, especially in the 3rd century once soldiers were permitted to marry.