In 1855 Sybil Dunbar came to Naperville as its first recorded black female resident; she died in 1868 and was buried in Naperville Cemetery on Washington Street. A commemorative marker honoring her was placed in the cemetery in 2015. After DuPage County was split from Cook County in 1839, Naper's Settlement became the DuPage county seat, a distinction it held until 1868. Naper's Settlement was incorporated as the Village of Naperville in 1857, at which time it had a population of 2,000. Reincorporation as a city occurred in 1890. In 1887, Peter Edward Kroehler established the Kroehler Manufacturing Company's factory in Naperville along the Chicago, Burlington & Quincy tracks. Kroehler Manufacturing became the world's largest furniture manufacturer, and a major employer in Naperville. The company closed the Naperville factory in 1978. In 1987, the site was redeveloped into upscale commercial and apartment properties, as Fifth Avenue Station. On April 26, 1946, Naperville was the site of one of the worst train disasters in Chicago history. Two Chicago, Burlington and Quincy Railroad trains, the "Advance Flyer" and the "Exposition Flyer", collided 'head to tail' on a single track just west of the Loomis Street grade crossing. The accident killed 45 and injured approximately 127 passengers and/or crew members. This event is commemorated in a metal inlay map of Naperville on the southeast corner of the Nichols Library's sidewalk area. In 2012, author Chuck Spinner published "The Tragedy at the Loomis Street Crossing" which details the tragedy and gives the stories of the 45 persons who perished. On April 26, 2014, a memorial entitled Tragedy to Triumph was dedicated at the train station. The sculpture by Paul Kuhn is dedicated not only to the crash victims but also to the rescuers at the site. A predominantly rural community for most of its existence, Naperville experienced a population explosion beginning in the 1960s and continuing into the 1980s and 1990s, following the construction of the East-West Tollway (now known as the Ronald Reagan Memorial Tollway) and Interstate 355 (originally known as the North-South Tollway, now the Veterans Memorial Tollway). It has nearly quadrupled in size as the Chicago metropolitan area's urban sprawl brought corporations, jobs, and wealth to the area. The March 2006 issue of "Chicago" magazine cites a mid-1970s decision to make and keep all parking in downtown Naperville free to keep downtown Naperville "alive" in the face of competition with Fox Valley Mall in Aurora and the subsequent sprawl of strip shopping malls.