In 1837, the University of Michigan was relocated from Detroit to Ann Arbor where the Ann Arbor Land Company had donated forty acres of land for the site of the university. This original forty acre campus was the area of Central Campus bounded by State Street, North, South, and East University Avenues. Buildings were first placed around the perimeter of campus, facing out to the city streets, beginning with four faculty houses in 1840, and the first classroom/dormitory building in 1841. Of those, only the President's House remains. The inside of the campus was kept as an undeveloped open space. By 1850, diagonal paths emerged, created by students and faculty walking from the corners across campus. These were soon covered with boardwalks and the major path became known as the Diag. In the 1850s, many trees were planted along the walks, giving more formality to the interior of campus. As the university grew, buildings began to occupy the interior of the site, such as the first library built near the center of campus in 1883. The Diag, now referring to the central open space, was more formally developed in the twentieth century, and continues to be the heart of the campus, and a major gathering spot. Generations of students have walked this same diagonal path as have countless respected faculty, alumni, staff, and visitors.