African Studies Center (University of Pennsylvania)
Africa Maps (University of Texas - Austin)
Map of a Journey to Musardu, the Capital of the Western Mandingoes / by Benj'n Anderson, 1868-69 (World Digital Library)
The Rediscovery of Africa 1400-1900: Antique Maps and Rare Images. William R. Jacobson. Stanford: Stanford University Libraries, 2004. ALEX REF DT17.J46
Maps and Mapping of Africa: A Resource Guide. John McIlwaine, comp. New Providence [NJ]: Hans Zell Publishers, 1997. ALEX REF Z6027.A2M38
The subject heading for maps is, you guessed it, "maps." You can do a subject search in the Library Catalog such as:
Tanzania -- maps
to find maps at Rutgers University Libraries. However, note that Rutgers does not have substantial holdings of African maps. Alternately, you can do an Advanced search for your keyword, selecting "Maps" from the Format drop-down menu.
You will also want to search for maps found in books. A book containing maps will almost always have a note in the catalog record that says, "illus."
Therefore, an Advanced Search such as:
subject keyword = Tanzania AND words anywhere = illus
will give us results such as these, all of which certainly contain maps:
Historical dictionary of Tanzania / by Laura S. Kurtz. Metuchen, N.J. : Scarecrow Press, 1978.
Ecology and change: rural modernization in an African community / by C. Gregory Knight. New York, Academic Press 
The geology of Kilimanjaro: [the results of the Joint Sheffield University-Tanzania Geological Survey Expeditions in 1953 and 1957]
Tanzania, a profile. New York, Praeger