A significant, later row house grouping, called Carstairs Row, was built in Philadelphia in 1800-01. William Sansom had bought a block of land between Seventh and Eighth Streets between Walnut Street and Sansom Street. Along Walnut Street Sansom built Union Row and along Sansom Street Thomas Carstairs built Carstairs Row. The rows, now part of Jewelers' Row, were block long rows of houses similar to row houses in the United Kingdom. The row houses were new to the United States as well and when built elsewhere in the country were called "Philadelphia rows". In the 1820s and 30s old buildings along the Delaware River were turned into tenements and factories, while houses a few blocks west were turned into stores. Several story high, brick row house continued to be built, many by Stephen Girard. At the same time granite fronts became popular in the city and marble mansions were constructed.