The network let the producers know ahead of time that season 4 would be the final season, so they were able to neatly wrap everything up.
You can watch Prison Break on Netflix, if you don't have it, Sign Up... it's a great site and you get a free Trial for something like 30 days, but you do have to use your Card Details. Still, the Subscription is really cheap, something like £6 P/Month, and it's got loads of other Dramas and Films on it like Breaking Bad, Etc.
As for the show itself. It's Brilliant, I've watched it a few times, one of the best I've ever watched.
Unfortunately it's one of those Serials that start of really good, but dies a horrible death. It's got four Seasons. 1, 2 and even 3 are absolutely Brilliant, but 4 is utter shite, and so is the Movie Special they made. They shouldn't have bothered. There's no Cliffhangers though.
This show is probably one of my favorite shows of all time. I was very satisfied with the ending. It most definitely was not a cliffhanger.
It was not Cancelled it ended because it was its time to end. It had a "proper" Ending
Having just come across a trailer on YouTube for this show, I really want to watch it but my research shows that it was cancelled after season 4.
Can someone please tell me if the show ended on a cliffhanger or did it have a "proper" ending, as I would hate to invest in a show that leaves unanswered questions or a cliffhanger etc.