The development or stagnation, regression of market towns can be interesting not only from the point of view of urban development for history or social sciences, but can also largely determine/reflect the life and possibilities of a given region, thus, the market towns themselves are closely related to the history of the region around them. The aim of my study is to outline the process during which the trajectory of a region that had been developing for centuries and had several urban settlements and market towns was broken, and the demographic and urbanization processes that had been noticeable within the region until then regressed and withered away. At the end of the review, I would also like to find an answer to why this phenomenon occurred. In the first half of the article, I present the demographic development of the region. There was no major break in the population of the Hegyköz settlements until the first third/middle of the 17th century, its population was approx. 10,000. After this, by the end of the Turkish era, the number of people living here decreased considerably (1692: 6,000 people). Then, in the 18th century, the area inhabited almost exclusively by Hungarians was repopulated with the help of a significant number of Romanians and a smaller Slovak and Swabian population, and in 1787 the number of inhabitants was already 18,000 (Hungarians made up approx. 70%). In parallel with the demographic and ethnic development of the population, the religious affiliation of the people living there also largely changed. While almost only Roman Catholics lived in the region until the Turkish era, in the 17th century, as a result of the rapid spread of the Reformation, the majority of Hungarians became Reformed. The majority of the Romanians, who appeared in large numbers during the resettlement, represented an Orthodox but growing Greek Catholic population, while the Slovaks and Swabians were Roman Catholics. The industrialization and modernization that took place in the second half of the 19th century had a positive effect on the number of people living here, which already exceeded 30,000 by 1910. In the 20th century, however, there was first a further increase of less intensity (1941: 34,196 people), then a large-scale decrease in the population. As a result, according to the data of the 2002 census, the number of inhabitants does not even reach 25,000, which corresponds to the level of 1880. Meanwhile, by the beginning of the 21st century, the number of Hungarians decreased to approx. 60%, and that of Romanians to approx. 36%. 75% of Hungarians are Reformed, 25% are Roman Catholic, and Romanians – as a result of the banning of Greek Catholicism in 1948 – are almost entirely adherents of Orthodoxy. Based on the demographic and historical geographical changes of the region, we can see that the settlements of the ’Bihari Hegyköz’, which played a central role in certain stages of the period between the 10th and 17th centuries, Bihar (Biharia), Adorján (Adrian), Szentjobb (Sâniob), Szalárd (Sălard), as well as Hegyközcsatár (Cetariu) and Micske (Mișca), halted in their development during and after the Turkish conquest. And after that, even though they kept their viability thanks to resettlement in the 18th century, they completely lost their central roles during the modernization that began in the last third of the 19th century, the disintegration of historical Hungary and the changing systems ofthe 20th century. Nagyvárad (Oradea), located in the immediate vicinity of Bihari Hegyköz, became the central place of the region.