The ball bounded off the tip end of the bat and went whirling along the first-base line.
The Crimson Sweater|Ralph Henry Barbour
Way bunted down the first-base line, and managed to beat out the throw.
The Lucky Seventh|Ralph Henry Barbour
On the first pitch, as Dreer got a fast start for second, Hollis bunted down the first-base line.
The Young Pitcher|Zane Grey
Andy did take his time, and as a result got four balls and walked to first-base.
The Putnam Hall Rivals|Arthur M. Winfield
He is entitled to first-base if the pitcher pitches four bad balls, at none of which he (the batsman) has struck.
Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 3|Various
British Dictionary definitions for first base
first base
noun
baseball
the base that a runner must reach safely to score a hit, and the first of the three bases he must reach safely on the way to home plate in order to score a run
the fielding position nearest this base
get to first baseinformal, mainlyUS and Canadianto accomplish the first step of an undertaking