After attending the University of Illinois at Urbana-Champaign for two years, in around 1875 McKinley worked as a drug-store clerk in Springfield.

[2] His re-election loss coincided with his service as national campaign manager for incumbent President William H. Taft, who also lost in 1912.

In 1926, he ran for re-election and lost to Frank L. Smith (who ultimately was denied the seat by the Senate on the grounds of fraud and corruption in his campaign).

[5] McKinley also was chief executive of the Illinois Traction System, an interurban electric railway.

The McKinley Health Center at the University of Illinois at Urbana-Champaign is also named for him.