Standing at the corner of a quiet Ontario street, the Post Office of St. Catharines presents an imposing Second Empire facade of dark red brick and rusticated limestone — its steep mansard roof bristling with iron cresting, its arched windows marching in three dignified rows above a grand entry stair with gas lamp standards still in place. Built in 1883 and still serving the city in this early-1900s view, the building anchors a streetscape that also includes a horse-drawn wagon at the curb and a glimpse of the "Post Office Book Store" sign on the adjacent brick building to the right. This hand-colored lithographic "Souvenir Mailing Card" — a format used in the United States and Canada between approximately 1898 and 1907, before the divided-back era — features the distinctive gothic-lettered "Souvenir Mailing Card" header on its undivided back, meaning all correspondence had to be written on the image side. The card is unused and clean, a fine example of the Private Mailing Card era.