Following graduation from high school, he travelled to Washington, D.C. to work as a distributing clerk of the Fiftieth Congress in 1887 and 1888.

In a special election held in February 1914, Vollmer defeated Republican Harry E. Hull, succeeding Pepper in the Sixty-third Congress.

Vollmer resumed the practice of law, while remaining active in local and state democratic politics.

He defended his brother, former county attorney Fred Vollmer, who had been indicted for allegedly assisting and abetting a conspiracy to violate the Espionage Act of 1917 by bringing a controversial League of Humanity speaker to Davenport soon after the United States entered World War I.

[9] Henry Vollmer's fiery speeches continued to attract criticism from his opponents and kudos from his supporters.