First of all, I strongly suggest you ignore any source that tells you Tae Kwon Do is 2000 years old. Korea may have a 2000 year-old tradition of martial arts, but Tae Kwon Do came to be in the 20th century.
As for good sources, you can start here at Korean Martial Arts resource:
http://www.martialartsresource.com/korean/korframe.htm
The least biased, and most thorough source of information there (and perhaps anywhere) is the book,
The Modern History of TaeKwonDo, by Won Sik Kang and Kyong Myong Lee. The version there is a very abridged version however. You may want to do a Google search to try and find a more extended .pdf version.
Since most paper resources you'll find will be biased towards a particular organization, I would suggest trying to research the histories of the major organizations and individuals in TKD's history. The WTF, the ITF, General Choi Han Hi, and Jhoon Rhee all have plenty of information written about them on and off-line. (You might also try looking up Son, Duk Sung, but there isn't much biographical information about him that I'm aware of.) I'm sure everyone else here can give you even more names.
Oh I almost forgot. Do a search in this forum for our previous discussions of the "history of TKD", and also for the "TKD FAQ". That should provide you with even more sources.