Andre Weil's "Two lectures on number theory. past and present." L'Enseignement Mathematique. Revue Internationale. fie Serie. 20: 87-110. 1974
available here http://retro.seals.ch/cntmng?type=pdf&rid=ensmat-001:1974:20::43&subp=hires
Great historical perspective on number theory up to the early 1970's. Easy to read too!
[I should remark that despite the article's great virtues, Weil is (apparently) unfair to Hardy and that many topics in number theory are left untouched.]