Cosgrove's research interests evolved from a focus on the meanings of landscape in human and cultural geography, especially in Western Europe since the 15th century, to a broader concern with the role of spatial images and representations in the making and communicating of knowledge. His work included how visual images have been used in history to shape geographical imaginations and in connection between geography as a formal discipline, imaginative expressions of geographical knowledge and experience in the visual arts (including cartography).
This broad concern was pursued through a series of focussed studies: of landscape transformation, design and images in 16th-century Venice and north Italy, of landscape writings by authors such as John Ruskin, of landscape, space and performance in 20th century Rome, of cosmography in early modern Europe (1450–1650), and of the history of Western imaginings of the globe and whole earth. He has also written extensively on theory in cultural geography and edited for six years the journal Ecumene (now titled Cultural Geographies) which publishes cross-disciplinary work on environment, culture and meaning.
Within his cultural research, Cosgrove differentiated between dominant cultures and alternative cultures. The dominant culture has the most influence in shaping a landscape. Most of what you see, he claimed, is likely to be a product of the dominant culture in a region. However, one is also likely to see evidence of alternative, or subcultures in the landscape. Within the category of alternative culture, Cosgrove differentiated between residual cultures (historic cultures that have disappeared or are in the process of fading away), emergent cultures (those that are just now appearing), and excluded cultures (those that are actively or passively excluded by the dominant culture).
In 2008, Cosgrove was awarded an honorary doctorate from the Tallinn University.[1] Cosgrove died of cancer at his home in Los Angeles on 21 March 2008.