sentences:  Many of the area's retail, jewelrymaking and appraisal businesses have been owned by the same families for five generations.Jeweler’s Row (Carstairs Row) was designed by builder and architect Thomas Carstairs circa 1799 through 1820, for developer William Sansom, as part of the first speculative housing developments in the United States, and introduction of the Row house in the United States.Carstairs Row was built on the southern part of the site occupied by "Morris' Folly" – Robert Morris’ unfinished mansion designed by Pierre Charles L'Enfant.