"WHAT DO YOU mean the mules pull the boat?" my 4-year-old son, Eli, asks. "Why don't they just have a motor?" Skeptical of our chosen mode of transportation -- a replica of a 19th-century canal boat -- our preschooler is not sure he's going to like a vehicle that doesn't have an engine or make loud revving noises. Personally, I'm not sure I'm going to enjoy a boat ride that doesn't involve a lido deck and a cool drink. But here we all are on a recent warm Sunday afternoon, my husband and two sons, riding a mule-fueled barge along the scenic C&O Canal in Georgetown.

The National Park Service has been ferrying folks along the C&O Canal in Georgetown on mule-drawn barges since 1976. The boats, reminiscent of the barges that traveled the canal during its heyday in the late 1870s, are floating history lessons powered solely by the sweat of park rangers' brow and mules.

Before boarding the flat barge, our sons, ages 8 and 4, came face to face with the mules: Brown-eyed beauties named Ada and Lil, who are horselike in size, with expressive eyes and long elegantly tapered ears. Visitors are invited to meet the mules, pet and nuzzle with them, pose for photos and ask all manner of mule-related questions. The most unusual question ever asked?

"How do the mules swim and pull the boat," says Patricia Brown, park ranger and canal boat guide, with a laugh.

For the record: The mules walk along the towpath, pulling the boat from shore the same way mules did more than 150 years ago. In fact, stepping aboard the Georgetown is like stepping into the 1800s. The passengers are greeted by Brown, who, although she is a park ranger, wears traditional 19th-century garb: full skirt and billowy blouse, topped off with a green apron and a jaunty wide-brimmed straw hat.

"Is everyone ready to go for a ride?" she calls out across the boat. The passengers respond enthusiastically, and it's difficult to tell who's more excited: the children or the adults.

"Repeat after me," Brown says. "A lock is an elevator for boats." The crowd chants this mantra several times as the gates are opened in the lock and the loud sound of rushing water -- about 100,000 gallons -- surrounds the boat. We slowly ascend about eight feet, a gentle and easy transition, not unlike the promised elevator analogy.

Rangers push the boat off with long poles, and the two-mule team crosses the scenic bridge and is tethered with tow ropes. Ada, we are told, is a bit skittish; a former farm dweller, she doesn't care for loud city sounds, her ears like twitchy antennas, responding to every horn honk and low-flying plane. Lil, the personable mule our children nuzzled with before the ride, was named for the last baby actually born on a canal boat, a girl named Lil, who was, strangely enough, named for her father's mule.

The mules are bred for strength and size, explains Brown, who reminds us that to make a mule, you need both a horse and a donkey. "An easy way to remember it is that the dad is always a donkey," she says. This gets a few giggles from some of the women on board.

The team works hard. The Georgetown is a 28-ton boat, and the mules pull it two hours a day, four days a week -- their historical predecessors worked much harder, it should be noted, pulling a 220-ton boat eight hours a day, seven days a week.

Brown explains that canal boat life was a family affair, describing the harsher realities of a world before child-labor laws and a working wage. Mothers, it turns out, were the central figures on the barges, literally at the helm, steering the boat, raising the children, cooking the meals and doing the laundry, mavens of multitasking even then.

The early canal barges were built for function, not comfort, and the Georgetown is a true replica in this respect. The original boats housed mules, tons of cargo and a family. Today, 85 passengers fit snugly, along rows of hard wooden benches, and in keeping with the historical interpretation, there is not a seat cushion or modern nicety -- snack bar, anyone? -- in sight.

Our history lesson continues as Brown compares barge trade to the work of today's 18-wheelers, having us imagine barges as the trucks of the waterways, delivering cargo up and down the canal. Traveling with Brown is like having your own personal history teacher on hand; a knowledgeable lecturer with an easy sense of humor, she delivers her message in a way that that both children and adults appreciate. In addition to her park rangerly duties, Brown is also an accomplished banjo player. She gives a brief history on the origin of the instrument before treating passengers to a short ditty, expertly plucking out a song by Stephen Foster. Many evening hours would be whiled away on the boat, listening to the strains of the banjo music, Brown explains.

There is a cool breeze on the water. Our older son listens in rapt attention as Brown spins tales of canal life and delivers a strong message about our stewardship of nature. My younger son is busy pointing out a family of ducks ahead of us and waving wildly to a pack of cyclists making their way down the towpath. Behind the walls of the canal, the busy streets of Georgetown are packed with traffic and pedestrians and the buzz of commerce, but all we can hear are the trill of birds as we glide along on our leisurely unmotorized pace, a floating refuge from the modern world. The trip takes an hour to go one full mile. Halfway there, up the canal without a paddle, we sit back and relax, and listen to the sounds of Ada and Lil clip-clopping steadily along, ready to guide us home.

MULE-DRAWN CANAL BOAT RIDES -- 1057 Thomas Jefferson St. NW. 202-653-5190. www.nps.gov/choh/BoatRides/PublicBoatRides.html. Through June 19: One-hour round-trip rides Wednesday through Sunday at 11 and 3; additional rides Saturday and Sunday at 1:30. Starting June 22: Wednesday-Sunday at 11, 1:30 and 3; additional rides Saturday and Sunday at 4:30. $8 for adults, $6 for seniors, and $5 for children ages 4 to 14. Other scheduled activities include free Georgetown walking tours every Saturday and Sunday at 12:15. Meet at the canal boats. Sunday, July 3 and July 16, free 19th-century music concerts from 1 to 1:30. Enjoy traditional folk music, played on banjo, concertina and flute, featuring popular songs of the era. Call to confirm as schedule is subject to change.

Costumed workers guide Ada, one of two mules that pull the Georgetown barge along the C&O Canal. Alex Kaufman meets the mules, which pull a 28-ton boat just as their predecessors did more than 150 years ago.