Control of Angel Mounds is transferred to the state of Indiana in 1946. but the Indiana Historical Society retained rights to excavate the site and Black remained on the property as its caretaker. Between 1958 and 1962, two National Science Foundation grants provided financial support to Black's efforts to apply geophysical applications to archaeological sites. Black and his student assistants tested a proton magnetometer's potential use in locating subsurface features at archaeological sites, extending the work begun by the University of Oxford's Research Laboratory for Archaeology and the History of Art. Black and his students traced segments of the palisade walls at Angel Mounds that were not visible from the surface. This project made Black among the first prehistorians to make "comprehensive tests in the Americas" to assess the proton magnetometer's potential on a New World site. Angel Mounds was designated a National Historic Landmark in 1964. In addition, his innovative excavation techniques were partially adopted by the University of Chicago Field School, one of the few training programs in archaeological field techniques in the United States in the first half of the 20th century.