A GeoHistoGram is a time line of sorts. It is oriented from top to bottom, the top being the newest time period and the bottom being the oldest time period. A GeoHistoGram shows layers across time and space. They can be used for any subject are across any grade level.
The below link is for a World GeoHistoGram
http://jacksoncisd.schoolwires.com/cms/lib/MI01000251/Centricity/Domain/36/GeoHistogramEmpires8x11.pdf
The below link is a lesson using a GeoHistoGram to track disease.
http://www.cst.cmich.edu/MGA/pdf/Disease%20Lesson%20%20Plan.pdf