There are two different sub species of white rhinos:  C. simum cottoni and C. simum simum.  C. simum cottoni which are northern white rhinos, are found only in the Democratic Republic of Congo.  C. simum simum are, as you can probably guess, are southern white rhinos and are mostly in South Africa with a small percentage lying in 7 other countries: Zimbabwe, Namibia,             Kenya,  Swaziland, Botswana, Democratic Republic of Congo, and Zambia. (map of Africa, library.sandiegozoo.org)

White rhinos like to be primarily in an open wooded area with a close grassland.  Water is also important and on occasion can be found around swampy regions.  A few trees are important because the rhinos will rely on them for shade, but they avoid big closed forests. 

As you can see in the map the yellowish area shows how extensive the white rhinos used to be in Africa compared to today's day and age.  The White rhino now only makes up a fraction of the area that they once covered.