For 100 years, the Mystic River Bridge has provided a vital link between the Stonington and Groton sides of the village.

An estimated 11,800 cars a day cross the bridge, which opens hourly or on demand to let boats pass beneath. Other than occasional frustration during peak traffic, the bridge is a marvel that is mostly taken for granted.

Consider, firstly, the feat of lasting a century.

Since its opening on July 19, 1922, how many other public works projects have lasted this long?

Similar in construction, the railroad bridge over the Thames River was built three years earlier, in 1919. But it was essentially replaced by Amtrak in 2008, when a new span was dropped over the existing piers.

Rhode Island's Jamestown Bridge was in use for 52 years before it was replaced; it was eventually demolished.

The Tappan Zee Bridge in Tarrytown, N.Y., was demolished 64 years after its construction.

Bridges are not built to last a century, which makes the Mystic Bridge's survival all the more remarkable.

It also was the first of its type.

Its Bascule construction, in which the bridge lifts upward using a system of counterweights and bull wheels, was a version invented by Thomas Ellis Brown, chief engineer at the Otis Elevator Co. This would be the first use of his design, which he patented in 1918.

The bridge is one of 54 Connecticut spans on the National Register of Historic Places, as part of the Mystic Bridge Historic District. It is not the only Bascule bridge listed, nor is it the oldest bridge on the list, although many are no longer in use.

The Mystic Bridge is worth celebrating not just for its utility and longevity, but what it represents.

It is, as The Day's John Ruddy described in his history of the bridge, published July 17, “the hinge connecting the village's two halves.”

What would Mystic be without this connection? Certainly tourists can reach the two halves by different I-95 exits, but something surely would be lost if a visitor to the Groton side could not easily cross to Stonington, and vice versa.

Community is made possible by connections. Although Mystic lies in two municipalities, those who live there identify as Mystic residents. The businesses, churches and other organizations that call the village home rely on that bridge to keep Mystic a whole entity.

Not to be discounted is the access the bridge affords for recreational boaters and vessels on the Mystic River, including those going to and from Mystic Seaport. They need the span to lift as much as drivers and pedestrians need it to fall.

The Mystic River Bridge is an engineering marvel that represents the best aspect of community living. Drivers wait in traffic so boats can pass; boaters idle below so cars can cross.

The bridge teaches us cooperation and patience. A century later, we need that lesson more than ever.