Stock Photo - The Margaret Hunt Hill Bridge is a bridge in Dallas, Texas which spans the Trinity River and was built as part of the Trinity River Project. Designed by Santiago Calatrava, it is one of three such bridges planned to be built over the Trinity; the second, the Margaret McDermott Bridge, is currently under construction. The span parallels the Continental Avenue Bridge, a walking bridge. . . The bridge is named for Margaret Hunt Hill, an heiress and philanthropist. . . Dallas is the ninth most populous city in the United States of America and the third most populous city in the state of Texas. The Dallas-Fort Worth metroplex is the largest metropolitan area in the South and fourth-largest metropolitan area in the United States. Divided among Collin, Dallas, Denton, Kaufman, and Rockwall counties, the city had a population of 1,197,816 in 2010, according to the United States Census Bureau.