Log Architecture
Scholars of log construction, the practice of building with hewn logs placed horizontally, one on top of the other, differ in their explanations of the origin of this practice in North America. McAlester and McAlester (1990: 82), who categorize log construction as being in the "Midland Tradition" of folk building customs, attribute the form to the Germanic immigrants who settled in the middle colonies (Pennsylvania, New Jersey, Delaware, and Maryland) during the early colonization period. Conversely, Hutslar (1992: 21-22) writes that the log construction practices were first introduced in North America by the Scandinavians, principally Swedes and Finns, who settled in the New Sweden area of the upper end of Delaware Bay in the mid-17th century.
With the influx of Scots-Irish immigrants, settlement spread from the middle colonies westward into central Pennsylvania and southward along the forelands and valleys of the Appalachian 
Mountains into Maryland, Virginia, the Carolinas, and Georgia. With no tradition of log building, the Scots-Irish were quick to adopt this style of construction that replaced the complex hewn framework of the traditional English house. Log building quickly became the common constructional mode on the boundaries of colonial settlement by the third quarter of the 18th century (Hutslar 1992: 22).
The lending of log construction to the familiar one-room deep, linear plan house with an external chimney, resulted in what McAlester and McAlester (1990: 84) term the "Midland log house." This form "was carried across the Appalachians . . . to become the dominant Pre-Railroad Folk housing over much of the heavily wooded eastern half of the county."
Log houses are generally comprised of room-sized, square or rectangular units called pens. The Midland house or single-pen dwelling is the most basic of log houses. Expansion beyond the single pen was problematic, as the strength of a log structure is dependent upon the joints of its four corners. Builders employed various methods of joining two units, which resulted in such plans as the "saddlebag," the "double-pen," and the "dogtrot." The need for additional space was also met with the development of three-unit and two-story forms, and with frame additions as cut lumber became locally available (McAlester and McAlester 1990: 84).
Distinctions are also made between log cabins and log houses. Generally, cabins are more temporary in nature and tend to be more crudely constructed. Cabins typically employ the use of rounded timbers that are joined at the corners by overlapping saddle notches, whereas log houses employ the use of square-hewn timbers joined by various hewn corner notching systems including square, V-notched, half-dovetail, and full-dovetail (McAlester and McAlester 1990: 36, 84). Hutslar (1992: 56, 76) notes that such distinctions between the two dwelling forms were made in the 18th and 19th centuries, and that "most settlers . . . were content with a log cabin only until they were able to provide a larger, more formal home."