Patches have been collected since ancient times. Greek and Roman pilgrims to pagan shrines made collections of miniature images of gods and goddesses or their emblems, and Christian pilgrims later did the same. Usually medieval Christian pilgrim Patches were metal pin Patches - most famously the shell symbol showing the wearer had been to the shrine of St. James at Santiago de Compostela in Spain. These were stuck in hats or into clothing and hard working pilgrims could assemble quite a collection, as mentioned by Chaucer in his 'Canterbury Tales'.
The growth in the 19th century of travel for ordinary people saw a huge increase in the souvenir industry, as these new secular pilgrims - like their medieval counterparts - wanted to bring back reminders of their holidays/vacations and sightseeing, ranging from china plates to postcards.
The production of stick-on souvenir Patches seems to have started in mainland Europe during the early 20th-century, probably in Germany shortly after the First World War when hiking became popular, and people began sewing Patches of resort towns onto their backpacks and jackets. In the U.S., the development of the National parks system and the growing popularity of vacationing saw a similar development of patch collecting.
After the Second World War, American GIs occupying Germany sent Patches back to their loved ones, showing where they were stationed. These Patches became known as sweetheart patches. They were also imported to Britain by Sampson Souvenirs Ltd., which also began producing Patches of British tourist spots, and went on to become (and still is) the largest British manufacturer of souvenir Patches. The biggest American manufacturer is Voyager Emblems of Sanborn, New York.
They are a good way of showing off places visited if worn on clothing, or stored in albums they can bring back memories of holidays/vacations or day trips.