My last trainning routine was made by myself and i had great gains on my back. Its more thick and defined...it was
Deadlifts
t-Bar rows on the corner
Dumbell rows
Pulldowns (with a close grip) on the front
Pulldowns with a wide grip, pulling to the back
shrugs...
The most effect ones for me was deadlifts and t bar rows...excellent exercises...Nowadays im not doing deadlifts anymore because i injured my lower back, but i do all the other exercises , but even like that i noted a difference in my back for worse already, after stopping deadlifts...

So i agree with a lot of people that say that probably the deadlifts is the major exercise for back. Just do it right and you will see results