The Changelings are not native to Altera, nor do they have any official settlement dedicated to their people. Their ability to alter their appearance also means that there is no telling just how many of the race resides upon Altera. Most of the population have no clue that they exist, a few rumors pass about in big cities of featureless faced creatures appearing after the death of some powerful being. Those that do know of their existence are powerful individuals that covet the services of the Changelings as spies and assassins.
As Changelings blend in, taking the face of another, they tend to stick to cities. Each major city is likely to have a contingent of Changelings, though no one outside their circle knows just how many.
Among the Changelings of Altera are stories of lands far off, a nation of their kind and the ancestors that found their way to Altera. Records and stories hint at Changeling agents at least 3,000 years ago, whether that was their first appearance or just the first they were documented in the secret histories of kings.
Unearthed Arcana Eberron