Peacemaker was originally created as part of Charltons comics line of "action heroes" and started out appearing in the back of "The Fightin' Five" by writer Joe Gill and artist Pat Boyette, first appearing in issue #40. He had two stories in Fightin' Five before it was canceled due to lack of sales, and Peacemaker was given his own solo series in 1967 with the same creative team. Like alot of characters in the 60s Peacemaker's stories were pretty much pulp and didnt have much of a over-arcing plot, though there were some recurring characters- mainly his Secretary Nora O'Rouke, though she only appeared in two issues before the series ended.
Christopher Smith was an American diplomat who by day would attempt to secure peace between nations through civil discussion, but in the instances where that didnt work out he would begrudgingly have to resort to other methods he certainly didnt take any joy in, but sometimes if you want peace, you have to fight for it!
So in sharp contrast to how he is portrayed today, Peacemaker was a straightforward superhero who was purely good. He would be thrown into semi-grounded GI Joe type scenarios where his enemies would often be other militarially involved humans (often people from Soviet nations) and monsters, and his goal would be to prevent war from breaking out due to some conflict or another. 
Peacemaker also had no superpowers and relied entirely on a large arsenal of military grade weapons he created himself, along with his own wits. He was described as practically a genius when it came to engineering and this was something often remarked by villains and allies alike. He attributed his genius to his parents, as his origin issue (issue #4 of The Peacemaker) explains, his mother was a "labratory researchist" and his father was "an army officer turned statesman". He went to school early, majoring in the sciences, and achieved many impressive scientific feats in his career before dedicating his life to his fight for peace.
Personality wise, Peacemaker was a respectable, rational man who could be expected to make the right hard decisions. He always thought on his feet and was portrayed as a wise figure whos words could be trusted, with constant allusions to his impressive diplomacy skills. He was also drawn as someone who was older in years, if his white sideburns were any indication.
Before Charlton went under Peacemaker only got one 5 issue solo series and seems to not have appeared in anything else until the acquistion of the Charlton comic characters by DC in 1986, by which point he would become a much different character. Probably the most interesting thing about this era of Peacemakers history is actually how often his current characterization still shines through: he is still reckless, often putting himself into the line of fire for one reason or another. He also of course still has a penchant for one liners and, obviously, his costume and powerset has remained mostly the same with minimal changes in the last half a century hes existed.
Also hes always been like that.
So Adrian Chase would come out of retirement as Vigilante, donning the costume again so he could kill Peacemaker and avenge the death of Dave Winston. They eventually meet up, have a battle that gets cut short by a news crew suddenly interrupting, and Peacemaker runs off into the night to appear 2 issues later in Vigilante #41, where he becomes convinced that Harry Stein is actually a terrorist who underwent extensive plastic surgery to hide his true identity. He attacks Vostok and Stein in Washington DC, and continues to pursue them until he is eventually stopped by Adrian, who wins the fight by knocking Peacemaker out, thus ending Peacemaker's introduction to the DC universe and leading into his characterization outside of Vigilante.