[1][2] After obtaining his bachelor's degrees, Monmonier started graduate school at the University of Maryland, where he worked with professors Azriel Rosenfeld and John Pfaltz.
[1][5] Monmonier's dissertation was titled On the Use of Digitized Map Sampling and Measurement: An Example in Crop Ecology, and focused on overlay analysis, building on his work with Azriel Rosenfeld and John Pfaltz.
As a graduate student at Pennsylvania State University, Monmonier was funded for three years as a National Defense Education Act Fellow.
Once the NDEA fellowship ended, Monmonir was funded at Pennsylvania State University as a teaching assistant where he ran lab sections for Physical Geography, and worked with Peirce F. Lewis.
[2] After getting his Ph.D., Monmonier began his academic career as Assistant professor of Geography at the University of Rhode Island in 1969, where he was hired to teach cartography and quantitative methods.
[2][1] He served in numerous roles in the American Association of Geographers, and on panels advising the National Research Council and the Environmental Protection Agency.
[11] He also wrote extensively on the use of maps for surveillance and as analytical and persuasive tools in politics, journalism, environmental science, and public administration.
[11] This is apparent in his most popular book How to Lie with Maps, which has been praised for explaining complex technical concepts in cartography in a way that is engaging and understandable to non-professionals.
[20] Kirby stated in a review that Monmonier's books have "shaped the way we think about maps, their uses, and their abuses, as well as their meanings in the world of business, international politics, and our everyday life.
His research and publications reflect this specialization, with work focusing on cartographic generalization, thematic map, and approaches to spatial analysis.
[2][22][23] Several of his publications relate to choropleth maps, including class breaks, intervals, and color choice as well as recommendations to avoid ink spread.
[3][11][26] The "Monmonier Algorithm", an important research tool for geographic studies in linguistics and genetics, is based on an article titled Maximum-Difference Barriers: An Alternative Numerical Regionalization Method.
[27][28] Monmonier's original article sought to find a "Maximum-difference boundary" by assessing how similar or dissimilar counties were with a common border.
[29] The 2004 Human Biology journal used Monmonier's 1973 algorithm to identify genetic barriers and visualize the spatial patterns of them, noting this method works where correlation analyses fails.