Prior to and during construction, three separate grants were issued by the National Park Service to document and recover artifacts of historical cultures along the river. These went to University of Utah historian C. Gregory Crampton and anthropologist Jesse Jennings, and to the Museum of Northern Arizona. Crampton subsequently wrote several books and articles on his findings. The Museum of Northern Arizona funded an expedition by William Miller and Helmut Abt, in coordination with the Navajo Nation, to investigate historical artifacts. They discovered a petroglyph in the upper part of the canyon depicting the appearance of the Crab Nebula in 1054.