The third president of the United States and considered by many to be the father of American archaeology because of his meticulous excavation of a Virginia burial mound. Jefferson was the first person, in North America or anywhere, to undertake (1784) excavations of a prehistoric site as a means to understanding the people who built it. He wanted to find out why the burial mounds on his land had been built. One mound he excavated carefully with trenches, noting that in a number of levels that skeletons had been placed in the ground and covered - producing a mound 12 ft (4 m) high. In observing the different levels, he was anticipating the stratigraphical method which became common practice in Europe and America only at the end of the 19th century. Worsaae's work in Denmark came a half a century later and the wider adoption of stratigraphical excavation methods was 100 years later.