Answered April 18th, 2019

Willie Mays breaks Ralph Kiner's 1949 NL record for home runs in a month with his 17th of August. Sammy Sosa currently holds the MLB record with 20 in June of 1998.

Which NL player was the first with 17 HR in a month?
Interpreted as:
Which NL player was the first with 17 or more HR in a month?