Conversation so far:
When did seabiscut get into racing?
1935.
Did he win his first races?
He failed to win his first 17 races.
When did Seabiscuit start winning races?
As a two-year-old, Seabiscuit raced 35 times (a heavy racing schedule), coming in first five times and finishing second seven times.

Question: Was he a well-known race horse?
Self-contained rewrite: Was Seabiscut a well-known race horse?