How Old Is This Barn?

How Old Is This Barn?. . There are three basic ways to date old buildings. First, documents can tell us when a structure was built or modified. Second, physical evidence, such as the way it was constructed, the materials used, and its shape and decoration, give valuable clues. For example, the original siding on this building was held in place with handmade wrought nails, suggesting a date before ca. 1820. Finally, scientific analysis of the tree growth rings in the wood used in a structure can tell us the year the trees were cut down. Tree-ring dating of this barn indicates that the original portion was built in the year 1785. It is one of the oldest wooden barns still standing in the state of Maryland. . . The central section of this structure is the oldest part dating from 1785. Originally, it had sheds on each side that protected the core building. These sheds were replaced several times and served a range of functions over the course of the barn's history. The current sheds are similar to the originals but were built in 2008. . . Clues From The Rings. . Living trees lay down annual rings showing each year's growth. Variations in the weather , wet, dry, hot, cool , create differences in the amount of annual growth. A science called dendrochronology studies the unique sequences of these rings to learn when a structure was was built. The sequence of narrow and wide growth rings from each year stretching back over centuries must first be established for a region. Scientists do this by removing small cores of wood from living trees and old buildings and then carefully matching up the rings. . . In the 1980s, scientists conducted the first major tree-ring dating study in the Chesapeake region. Focusing upon Southern Maryland, they sampled 64 trees and 24 buildings, and created a sequence spanning 410 years from 1570 to 1980. The wooden timbers in this barn tell us it was constructed in A.D. 1785, and the wide floorboards were added in A.D. 1848. Results of this tree-ring study surprised everyone. Many structures believed to be of 17th-century date were actually built in the 18th century. These findings changed our understanding of the architectural history of this region. . This historical marker was erected by Historic St. Mary's City. It is in St. Mary's City in St. Mary's County Maryland