Other government agencies should take a cue from the NIH, which has started to edit Wikipedia pages relating to health issues: http://nihrecord.od.nih.gov/newsletters/2009/09_04_2009/story2.htm
When a small amount of information is added to Wikipedia, it is like planting a seed; other people come along and add water, and everyone shares the fruit. Wikipedia editors today have high standards; they write professionally and they believe in citing all their claims.
Even if the department of state did not edit wikipedia itself, it could share a lot of its historical research, and that information could be added to wikipedia, just as CRS reports have been added. (To give you an example of what can be done: Here is a partial list of Wikipedia articles into which I've incorporated content from CRS reports: http://en.wikipedia.org/w/index.php?title=Special:WhatLinksHere/Template:CRS&limit=1000 . For example, this summer I made a Wikipedia article out of every item in the CRS's glossary of agricultural terms: http://ncseonline.org/nle/crsreports/05jun/97-905.pdf )