Final answer:
The sentence in question is a compound sentence because it includes two independent clauses joined by the conjunction 'and'.
Step-by-step explanation:
The sentence "Jackie Robinson was the first African-American big league player, and he helped his team win the World Series." is a compound sentence. A compound sentence contains at least two independent clauses joined by a conjunction. In this case, there are two independent clauses: "Jackie Robinson was the first African-American big league player" and "he helped his team win the World Series," which are joined by the conjunction "and".