The D.A. was first authorized in 1970 by the Committee on Graduate Studies of the American Association of State Colleges and Universities, and by the Council of Graduate Schools in the United States. The prestigious Carnegie Foundation was the first to fund ten universities with seed money to initiate the degree, and D.A. programs (though far fewer in number than those of the Ph.D.) are currently offered in many different disciplines at universities in the United States and in other parts of the world.
The D.A. differs from the Ph.D. in its shift in emphasis from theoretical research (though research is required) to the advanced study of a specific discipline, content area expertise, learning theory, and curriculum design. As such, it is often described as a "teaching doctorate". It offers scholars the breadth and diversity necessary to become expert teachers in their field. The D.A. also differs from the Ed.D. in its strong disciplinary focus, while still embracing the Ed.D.'s concern for issues in education, and a theoretical as well as practical preparation in pedagogy. (For more on this issue, see Ph.D)
While the Ph.D. is the most common doctoral degree, and even often (mis)understood to be synonymous with the term “doctorate,” the U.S. Department of Education and the U.S. National Science Foundation (NSF) recognize numerous doctoral degrees as equivalent in status, and do not discriminate between them.
A list of doctoral degree designations can be found at: doctorate.