Beyond the interstate underpass, Chestnut Street becomes a street of industrial buildings which provides an introduction to the Jewelry District. If Samuel Slater represents the technological progenitor for Rhode Island's textile industry (see under Pawtucket), so Nehemiah Dodge stands in the same position for the Providence-centered costume jewelry industry. In his Providence jewelry shop in the late 1790s, Dodge discovered a process for plating silver and gold to base metals, thereby providing the industry's foundation. A tight area, the Jewelry District is mostly concentrated within the interchange loop of Interstates 95 and 195, although somewhat contracted from its onetime extent. The small size and high value of the product encouraged small-to-medium-sized factory units. Located here until well into the 1960s and 1970s in straightforward, handsomely proportioned brick construction, they are worth study as a group. As portions of this industry have disappeared or moved to more open sites, many of the buildings left behind have been converted to office, apartment, and studio use, although manufacturing continues in some of them. Notwithstanding the spread of the industry around the area (and increasingly outside it), Providence is still the national center for costume jewelry, to which buyers make biannual treks to inspect displays at two wholesale markets.