There's this timeline that was started on
http://historyofbitcoin.org/, quite a lot of useful dates to make note of, for me particularly, the dates Bitcoin value was first established on an exchange (October 5 2009) and quote:
New Liberty Standard publishes a Bitcoin exchange rate that establishes the value of a Bitcoin at US$1 = 1,309.03 BTC, using an equation that includes the cost of electricity to run a computer that generated Bitcoins.
Also when it reached parity with the US dollar, if price tracking is important (it's not, but significant).
The timeline ends abruptly in 2014, but it was resurrected here, all the way to March 2017:
http://www.therevolutionwillnotbecentralized.com/timeline/This shows bigger picture:
https://timelines.issarice.com/wiki/Timeline_of_Bitcoin