[1] The subject matter of his work includes but has not been limited to street performers, musicians, barflies, historical scenes, landscapes and building structures.
[2] Lauded in Europe but widely unknown in his native Chicago, Guinan's work reflects a documentary quality that has been compared to "that of the Parisian demi-mondes as chronicled and interpreted by Toulouse-Lautrec.
Guinan's work has been featured in exhibitions as follows:[4] "Oeuvres des années soixante", Galerie Albert Loeb, Paris; "Peintures et dessins", LARC, scène Nationale, Le Creusot.
Times writer David F. Lane wrote in 1950 that his paintings were "of such character in composition, coloration and brush technique as to definitely forecast a promising future for him in the field of art."
He praised the 16-year-old artist's "rare genius for capturing action in tense moments, and in rendering facial expressions which accurately represent the mood and thought of the character.
[11] He also discovered Maxwell Street, an open-air market which had been a Chicago tradition since the beginning of the century; once dominated by Jewish merchants, it was now popular with African American peddlers and Blues musicians.