1578 Kirkwood, provisional designation 1951 AT, is a Hilda asteroid from the outermost regions of the asteroid belt, approximately 52 kilometers in diameter. It was discovered on 10 January 1951, by astronomers of the Indiana Asteroid Program at Goethe Link Observatory in Indiana, United States.^[3] The asteroid was named after American astronomer Daniel Kirkwood.^[2]

Kirkwood belongs to the orbital Hilda group, which is located outermost part of the main belt.^[4] Asteroids in this dynamical group have semi-major axis between 3.7 and 4.2 AU and stay in a 3:2 resonance with the gas giant Jupiter. Kirkwood, however, is a background asteroid and not a member of the (collisional) Hilda family (101).^[5]

It orbits the Sun at a distance of 3.0–4.9 AU once every 7 years and 9 months (2,839 days). Its orbit has an eccentricity of 0.24 and an inclination of 1° with respect to the ecliptic.^[1]

The asteroid was first observed as 1944 DF at Turku Observatory in February 1944. The body's observation arc begins with its observation as 1949 TF at Heidelberg Observatory in October 1949, fifteen months prior to its official discovery observation at Goethe Link.^[3]

In the Tholen classification, Kirkwood is a dark D-type asteroid.^[1] It is also characterized as a D-type by PanSTARRS photometric survey.^[10]

This minor planet was named in memory of American astronomer Daniel Kirkwood (1814–1895), long-time professor of mathematics at Indiana University. He discovered the Kirkwood gaps, which are gaps in the distribution of the mean distances of the minor planets in the asteroid belt. Kirkwood was the Indiana Asteroid Program's first numbered discovery.^{[2][lower-alpha 2]} The official naming citation was published by the Minor Planet Center in March 1952 (M.P.C. 738).^[11] The lunar crater Kirkwood was also named in the astronomer's honor.^[2]