A painter and widely published magazine illustrator, he gained prominence for his architectural work such as in the 1906, Plan for Chicago, and for the large murals he painted in many well-known public structures such as the Lincoln Memorial.

His first major break occurred when he was hired by Charles Follen McKim to create some illustrations for the Senate Parks Commission (McMillan Plan) for Washington.

[4] As a result of his success in Washington, Daniel Burnham and Edward Bennett hired Guérin to make perspective illustrations for their monumental work, The Plan of Chicago in 1907.

In 1912, when the architect Henry Bacon was competing with John Russell Pope to win the commission for the Lincoln Memorial in Washington D.C., he hired Guérin to create renderings of alternative designs.

After he received the commission, Bacon retained Guerin to paint two large murals, Reunion and Emancipation, that decorate the cella of the memorial above the Gettysburg and Second Inaugural Addresses.

Unlike previous fairs, this west coast effort used a palette of Mediterranean colors to accent the buildings to take advantage of the local climate and flora.

It is likely that connections that he made there led to his one-man show at the University of California, Berkeley two years later, followed by several large murals in the old Federal Reserve Bank Building of San Francisco.

Indeed, he stands tall among a distinguished group of American artists who brought to life the scenes and buildings of the Progressive Era in the emerging print media of the early Twentieth Century.