Once upon a time a one-ounce Hershey bar cost a nickel. That was in 1950. Everyone knows that M & Ms melt in your mouth and not in your hands. And on at least one Valentine's Day we've all received a red heart-shaped box filled with silver-wrapped chocolate kisses.

Ultimate responsibility for such nostalgia rests with the Hershey Food Corp., which has a home nestled in the hills and valleys of Pennsylvania's southeastern countryside only a three-hour drive from Washington.

Naturally, the No. 1 item on the agenda for any visitor to Hershey, also called "Chocolate Town, USA," must be the factory where these confectionary delights are produced. This is the best bet for kids, too.

Unfortunately, for health reasons and because the sheer volume of visitors became prohibitive, the original plant tour is no longer open to the public. No more vats of chocolate bubbling just beyond a glass partition, no more free samples.

But don't despair. Now there's Chocolate World on Park Boulevard, open Saturday 9 to 5 and Sundays noon to 5. A 10-minute tour by automated conveyor takes you through simulated tropics, then to shipping docks and factories and through production of the familiar chocolate bar. You sit in a five-person vehicle and listen to the guided tour replete with jungle sounds, a trip through a roaster in which you actually feel heat and, in summer, smell the chocolate. At a giant concession stand, chocolate shoppe and tropical plant display, you can browse at leisure.

Autumn is perfect for a day's jaunt or a weekend at Hershey. Although Hershey-park (a giant theme park) closed last month, there's a tram tour through it for $1.25 (children under 5 free). This 15-minute ride includes a stop at the 330-foot Kissing Tower to view the 65 acres from on high. I prefer to avoid crowds, so this minidose of a theme park is just right.

If the Kissing Tower isn't high enough, Hershey Airpark offers rides in Piper Cherokees at $5, ($4 for children under 10).

Wander through town and check out streets named Hava, Cocoa and Chocolate. The street lights are made in the shape of Hershey's kisses some in a silverfoil wrapper, some unwrapped.

Hotel Hershey, older and more elegant, with formal gardens and an ecticing Spanish decor, offers a similar "Freedom Weekend." And its circular dining room offers excellent cuisine. Although the menu is constantly changing, an example of dinner items includes lobster tail and Long Island duckling, plus the ever-present chocolate cake, chocolate cream pie and creamy cocoa pudding (what else?) for desert.

For exercise, riding stables, five golf courses, tennis and indoor swimming are all available. Or you can play shuffleboard, then stroll through the rose gardens, see the flags honoring the seven countries most noted for the hyrbridization of roses. Then wander down to the pond and watch the ducks and swans surround the "Boy With the Leaking Boot" - one of 23 such statues in the world - which has a hint of mystery. The gardens and arboretum are open Saturdays and Sundays from 8 until dusk (admission $1.25).

For the history-minded, the Hershey Museum of American Life offers items from Pennsylvania's history plus a collection of Indian and Eskimo artifacts. An apostolic clock performs at a quarter to each hour, and there's a slide show on 18th-century farm life at a quarter past each hour. Mostly you'll want to study the handmade quilts, carved wood items, china and Stiegel glass on display. Open Saturdays and Sundays 10 to 5, but closed during December.

If the children are along, you might want to buy a few Hershey bars for the ride home - even though they now cost 20 cents for 1.2 ounces of the milk chocolate - for there are few restaurants on I-83.