Locations in Houston are generally classified as either being inside or outside Interstate 610, known as the "610 Loop" or simply "The Loop". Inside the loop generally encompasses the central business district, and has come to define an urban lifestyle and state of mind. Elizabeth Long, the author of the 2003 book "Book Clubs: Women and the Uses of Reading in Everyday Life", wrote that most of the upper middle classes in the 610 Loop live in the southwestern part of the inner city in the areas near Hermann Park, the Houston Museum District, Rice University, and the Texas Medical Center, while some portions of northern Houston and Eastern Houston have been gentrified and also have upper middle classes.