LANCASTER, Pa. -- Throughout its history -- from the lone American Indian on foot to boatloads of tourists -- the Susquehanna River has been subject to trade-offs.

The massive flow of its water became the natural resource of choice during the development of the United States in the 20th century. In 1904, the York Haven Power Co. (now a GPU Energy company) completed the first hydroelectric damming of the Susquehanna River at York Haven, marked by the mouth of the Conewago Creek.

In the next 30 years, larger dams were built downriver at Safe Harbor, Holtwood, and Conowingo.

Today, the Susquehanna's 40 miles -- the section that forms the border of Lancaster County -- between the Conewago Creek and the Chesapeake Bay host one of the heaviest concentrations of electricity-generating units in the world, according to Jack Brubaker's 2002 book, "Down the Susquehanna to the Chesapeake."

The four dams take control of the water that flows between York and Lancaster counties to the Maryland line.

These dams redefine the natural outline of the river and they create basins of silt, a problem that will need to be addressed well within the next 30 years.

Yet they give us amazing recreational opportunities, specifically named Lake Frederic, Lake Clarke, Lake Aldred and the Conowingo Pond.

So now, turn out the lights and plug in the crock pot and the answering machine, and let your electrical appliances do your work while you go out and enjoy the lakes of the Susquehanna.

Pick up your paddle or your oars, perhaps your fishing pole. Put on your bathing suit or your hiking boots. Or maybe you just want to get in the car and follow the River Road (Route 441) to enjoy the views.

Here are just a few of the high points:

* Lake Frederic is a 4-mile lake defined roughly by the town of Royalton and downstream to York Haven Dam. Above Royalton, the river is subject to security restrictions on Three Mile Island and near Harrisburg's airports.

This most urbanized section of the river includes islands large enough to permit farming and summer communities.

Fishing is said to be fabulous near Falmouth, and swimming is said to be good on the Goldsboro side of the river. But the best fishing and swimming holes are secrets to be hoarded and open to exploration.

* York Haven to the Columbia-Wrightsville Bridge is a river space between two lakes. It holds many natural and manmade wonders, such as Susquehanna Aquacultures, a commercial fish farm, accessible from the York County side of the river. You can buy fresh fish for supper here.

The Mason-Dixon Trail comes close to the shore in several natural sections here. It is tough and rocky walking so consult the trail guide or the Web site www.angelfire.com/pa2/yorkhikingclub/mdts.html for current conditions and re-routings.

At Haldeman Mansion at Bainbridge, you can imagine yourself living along the river in the 18th century. Stroll the lawn and enjoy the shade of the same large trees that began life here back then.

Marietta bears all the characteristics of an old river town. Much mansion-gawking can be done here.

Chickies Rock Overlook is a short walk from the River Road (Route 441). In late winter, you might spy snow geese fishing among the riffles.

Wrightsville offers a large, easily accessible boat launch area next to the outdoor lunch patio at the John Wright Factory.

Stroll across the old bridge between Columbia and Wrightsville, where citizens regularly scouted romantic liaisons or strolled to enjoy the river breezes before the days of air conditioning.

Wright's Ferry Mansion, home of Susanna Wright, who emigrated to America soon after her birthday in 1698. The house has been carefully restored and holds antiques created by Philadelphia cabinetmakers for the wealthy British immigrants of the time, along with an early American kitchen and signs of Susanna Wright's accomplishments, among them the raising of silkworms and the spinning of silken fibers to make garments for her friends, such as Benjamin Franklin.

* Lake Clarke is a 10-mile lake formed by the Safe Harbor Dam and defined to the north by the Columbia-Wrightsville Bridge.

If you have your own sailboat, join the Susquehanna Yacht Club at Long Level. If you have your own canoe, join the Conewago Canoe Club, flat water division, that puts onto the river from the Wrightsville Launch area every Tuesday.

The Conejohela Flats off Washington Boro is a premiere spot to see any of 250 species of shore birds that have been catalogued here. Viewing is year-round and may include nesting bald eagles, tundra swans, snow geese and the smaller migratory birds such as grebes, harriers and marsh wrens.

Turkey Point is a land mass that defines the narrowing of the river as it turns south and leads to the gorge of the Susquehanna. You can hike to this overlook, winding your way past the manmade landfill, a well-managed compost with a certain kind of beauty in sculptured textures created by man using modern methods of burying our trash.

Stop at Shank's Mare for an ice cream cone on the porch and a winter view of the turkey gobbler profile (Turkey Point) on the opposite shore.

* Lake Aldred is formed above the Holtwood Dam, with the Safe Harbor Dam at its northern boundary. This 8-mile lake touches some of the most rugged and beautiful ups-and-downs of the southern river hills, among them Wind Cave and House Rock just below Pequea.

Wildflowers bloom as far as the eye can see at Shenk's Ferry Wildflower Preserve. Hepatica begin to bloom as early as February in these sheltered gentle hills. Flowers peak in April.