Lime is a white, powdery substance widely used in construction, agriculture, and industry. It is manufactured by heating limestone. Small amounts may be produced in an open fire but more effectively when enclosed. Early pits were lined with stone and in time enclosed in an oven or kiln. The 19th-century lime kiln, of Roman design, was a large "pot" dug into a hillside, surrounded by a stone box resembling a huge fireplace. Many thousands were built in the Susquehanna River valley. During settlement of "Penn's Woods," large tracts were subdivided many times, and by 1925 we find 12,000 farms in Lancaster County alone, and nearly every farmer wanted to produce his own lime to sweeten the fields and make mortar, plaster, and whitewash. In the most recent record, the 1875 county atlas, we find more than 500 kilns, a peak time for "do it yourself" lime burning. Commercialization relieved the farmer of the hard and dangerous work of lime burning, and the kilns fell idle around the turn of the century. Today we find evidence of 128 extant kilns in the county. Some are little more than remnants of former stonework, but others remain sturdy and sound. Their photos in this book reveal the art and labor of our ancestors who played a major role in the development of our nation.