McElroy was born in Berlin, Wisconsin (in Green Lake county), on January 8, 1856.
In 1886, he was elected for the Assembly's 4th Milwaukee County district (the Fourth Ward of the City of Milwaukee) as a Republican, with 1,444 votes to 1,335 votes cast for Timothy Cruice, Democratic and People's Party nominee, and 71 votes for Prohibitionist W. A. Arnold, succeeding fellow Republican Robert W. Pierce.
[2] He was not a candidate in 1890, and was succeeded by another Republican, Orren Thomas Williams.
He was appointed to a three-year term on the University of Wisconsin's Board of Regents by Governor Robert M. La Follette; he also served on the university's Board of Visitors, and as president of the Milwaukee bar association.
This article about a Republican Party member of the Wisconsin State Assembly born in the 1850s is a stub.