As tensions escalated between the North and South during the 1850s, stationers began to issue envelopes for sale containing patriotic illustrations and verses. Flag motifs were especially popular. As most of the printers of the envelopes were located in the North, the majority of the output favored the Union cause. However, printers in border states such as Maryland produced envelopes to appeal to both Northern and Southern audiences. The popularity of illustrated envelopes waned about 1863 as they became too expensive to produce in a time of war.