Scotland a territorial parish structure, with every community in Scotland having a local congregation. Scotland also has a significant Roman Catholic population, 19% professing that faith, particularly in Greater Glasgow and the north-west. After the Reformation, Roman Catholicism in Scotland continued in the Highlands and some western islands like Uist and Barra, and it was strengthened during the 19th century by immigration from Ireland. Other Christian denominations in Scotland include the Free Church of Scotland, and various other Presbyterian offshoots. Scotland's third largest church is the Scottish Episcopal Church. Islam is the largest non-Christian religion (estimated at around 75,000, which is
Geography of Scotland in the Middle Ages burghs, the late Middle Ages saw the proliferation of baronial and ecclesiastical burghs; 51 were created between 1450 and 1516. Most were much smaller than their royal counterparts, and excluded from international trade they acted mainly as local markets and centres of craftsmanship. There are almost no written sources from which to re-construct the demography of early medieval Scotland. Estimates have been made of a population of 10,000 inhabitants in Dál Riata and 80–100,000 for Pictland, which was probably the largest region. It is likely that the fifth and sixth centuries saw higher mortality rates owing to the appearance of