The 2001 World Series telecasts (New York Yankees vs. Arizona Diamondbacks) claimed the largest U.S. TV audiences in recent memory: 24.5 million viewers per telecast, on average. 
But the late Seventies and early Eighties remain the true glory days of World Series TV viewership.
The 1980 World Series telecasts — the last time the Philadelphia Phillies won a World Series — drew the largest per game TV audiences on record: almost 54.9 million average viewers.

Baseball fans across the country might have been a little sleepy Friday morning after watching the Boston Red Sox’ late-night comeback victory against the Tampa Bay Rays in Game 5 of the MLB American League championship Series.
The game, in which the Red Sox trailed the Rays by seven runs as late as the seventh inning, was a rollercoaster ride for both teams’ fans — as reflected in the preliminary metered market TV ratings, released by Nielsen on Friday.
At the close of the game’s first hour, one-quarter of all Boston households were watching, …