Polly Plummer was created in 1955.
No. The heroine of The Silver Chair is Polly Plummer.
Plummer Building was created in 1926.
Plummer Additional was created in 1891.
Plummer Memorial Library was created in 1927.
Polly Peck was created in 1940.
Polly - novel - was created in 1998.
Polly-O was created in 1899.
Polly - Doctor Who - was created in 1966.
Polly Becker was created in 1997.
Polly Tones was created in 2008.
Plummer Family Helluva Handball Bash was created in 2008.
There are, you could argue, two main characters in the book: Digory Kirke and Polly Plummer. Digory is in more of the book than Polly though. Also since it's called "the magicians nephew" and Digory is the magicians nephew he is a bit more of a main character than Polly.