Hundreds of illustrated envelopes, known to collectors as “covers,” have lasted a century or more, almost in spite of themselves. And although nothing is more disposable than an envelope, the now forgotten correspondents of the 1850s and 1860s who mailed the examples seen here took great pains with them. One sender selected a printed patriotic motif to send to Prussia, while another drew a scene in lively detail, filing his small-scale canvas and incorporating both stamps and address in the design. And what functioned in its time as an ordinary trademark—the stamp of the Pony Express—now stands as a rare survivor of the short-lived overland mail run, able to fetch thousands of dollars at auction.

—C.D.