ST. LOUIS, Mo. — A stamped envelope, designed for the St. Louis Stamp Expo, marked more than 200 years of the Soulard Farmers’ Market, one of the country’s oldest open-air markets.

The envelope, called a cachet, was designed and illustrated by Tom Minor, a St. Louis architect and stamp collector. “The cachet topic is selected by committee, and someone mentioned the theme of sustainability for this year,” he said. “The Soulard Market seemed like a good fit.”

Minor has designed the Expo’s cachet for the past 20 years.

The Soulard Market is in a St. Louis neighborhood listed on the National Register of Historic Places. Minor’s design includes color artwork of the market and a dated, black-and-white illustration of Soulard Market Station. Cachets were printed for each day of the Stamp Expo, March 27-29.

A first-class U.S. stamp, from a four-stamp issue commemorating farmers’ markets, is affixed to each cachet. “It just so happened that the farmers’ market stamps came out last spring, so they were perfect for the cachet,” Minor said.

The stamp designs feature products found at farmers’ markets – sunflowers, produce, breads, flowers and herbs.

Vera Felts, from Carterville, Ill., said the farmers’ market stamps are among many related to agriculture. “There are also farmers’ market stamps from Malaysia,” said Felts, executive director of the American Topical Assoc., which promotes thematic stamp collecting and study.

The group offers different stamp study series, including ones focused on tractors, grains and other farm and food topics.

Stamps are like “windows into the world,” said Felts, who grew up on a western Illinois farm. “Stamps are a way you can learn about different cultures of the world, including the way farming is done in those countries.”

Information on her group is available online at www.americantopicalassn.org

Tom Minor started collecting stamps topically 23 years ago; the architect found himself buying stamps with buildings on them when his 10-year old son started a stamp collection. This year’s St. Louis Stamp Expo Youth Room hosted hundreds of area students and Boy Scouts, who could work on their stamp collecting merit badge at the event.

The Stamp Expo included more than 40 stamp dealers, 30 juried stamp displays and a two-day auction. Information on the expo, which is each March or April, is available at www.stlstampexpo.org