Researcher Art Champoux has a good piece on UFO Digest on the history of MIBS in this country:Extraterrestrials in America's History.
For more interesting background on the MIBs, read William Bramley's The Gods of Eden.
Also, for a more academic look, see The "Men in Black" Experience and Tradition: Analogues with the Traditional Devil Hypothesis
by folklorist Peter M. Rojcewicz for The Journal of American Folklore, Vol. 100, No. 396 (Apr. - Jun., 1987), pp. 148-160 (article consists of 13 pages) You have to be an academic or pay to get this on-line, fortunately I still have this from my college days.
Just for fun, this image of James Cagney from the classic Public Enemy, while having nothing to do with MIBs, just gives the MIBS creeps!