When the Browns moved from the AAFC to the NFL, they won the first eight meetings between the Steelers. The Browns would win three championships in the '50s (1950,1954,1955), and another in 1964.
Soon enough, the Steelers started to fight back and evened up the records under Chuck Noll, who was a former Brown.
In 1970, the AFL merged with the NFL. This caused the NFL to split up into the AFC and NFC. Former Browns owner Art Modell volunteered the Browns for the AFC so they could have an intrastate rivalry with the Cincinnati Bengals.
Modell was able to convince Art Rooney to join him and continue the rivalry. The Steelers would win four Super Bowls in the '70s.
While the teams would exchange victories in the 1970s and 1980s, the Steelers would gain control by the 1990s.
Since the last series sweep by the Browns in 1988, the Steelers are 26-8 and have finally passed the Browns on the all-time series lead. Lead by Head Coach Bill Cowher, another former Brown and assistant under Marty Schottenheimer.
The Steelers are also 2-0 against the Browns in the playoffs; both games were played in Pittsburgh.
After the Browns returned to the NFL in 1999 (Modell moved the team to Baltimore), the series has been all Steelers.
I believe the rivalry would have died if both of the fanbases weren't the most hardcore in the league.
The Steelers have won nine-straight games against the Browns. Cleveland came close to breaking that streak last year.
Is this the year the Browns take back the rivalry? Only time will tell.