He also taught in the schools of Anne Arundel County, and studied history and political science at Johns Hopkins University in Baltimore.

In 1898, he married at Emmanuel Protestant Episcopal Church of Baltimore as his second wife Helen Aletta Perry (1868–1944), widow of wealthy jeweler Gilbert D. Clark (d. 8 Dec 1896) and daughter of a prominent medical doctor.

Linthicum's most important role in Congress was that of the leader of the Wets (those who advocated the repeal of alcohol prohibition), succeeding John Philip Hill in 1927.

Working with Republican James M. Beck of Pennsylvania, Linthicum co-wrote and in 1932 introduced the Beck-Linthicum Bill which was designed to repeal the 18th Amendment.

In 1918, Linthicum was motivated by his wife Helen a noted "club woman" and by Mrs. Reuben Ross Holloway, to become the first to introduce a bill which would make the Star Spangled Banner the official national anthem of the United States, though it was not made so until 1931.