Forgive me if this has been covered but Wikipedia has a great history of EMD. Just Google EMD. It covers early inception in thte 1920's, through F units, geeps, the incredibly successful SD-40-2 era of the 1960's, later SD models, right up to being sold in 2005. Sadly after that EMD were not able to get their 710 series engine Tier 4 certified, so they could not sell locomotives in mainland US afterwards.
It's as great read.
