This year marks the 50th anniversary of the seaway’s opening, which literally connected the Great Lakes to the rest of the world. Celebrations are planned throughout this weekend at the Dwight D. Eisenhower Visitors’ Center in Massena, N.Y. They will honor the seaway’s historic role and its ongoing vitality–and also remind us about the economic importance of infrastructure projects that promote international trade.

It might be said that work on the St. Lawrence Seaway began in 1680. That’s the year the seaway’s website credits Dollier de Casson with beginning an effort to build a canal around the rapids of Montreal. He wouldn’t live to see his work finished. Neither would any of his contemporaries. It took until 1824 before a five-foot-deep canal was completed.

It goes to show that early on, people understood the necessity of opening the vast inland seas of North America. Serious discussions to embark on a major construction project began in the first years of the 20th century.

Unfortunately, special-interest lobbying from railways and U.S. ports forced numerous delays. Some things never change: The influence peddlers will always be with us, and their self-serving demands always must be overcome.

By the early 1950s, the Canadians announced that enough was enough: They were going to build the seaway with or without American help. This prompted the United States finally to get on board. Work began in 1954. It took five years. The seaway was formally opened in 1959 by President Eisenhower and Queen Elizabeth II, when they enjoyed a short cruise through a portion of the seaway aboard the royal yacht.

Since then, more than 2.5 billion tons of cargo, worth more than $375 billion, has gone up and down the seaway. Farmers in the Midwest have relied upon this outlet: This is how they’ve exported much of their grain to foreign buyers. Other commodities, such as iron ore and coal, also have depended upon the seaway. About one quarter of all seaway traffic involves a distant port in Europe, the Middle East, or Africa.

The St. Lawrence passage is so important that it has led to its own ship classification: Seawaymax. Just as Panamax ships are specifically designed to move through the Panama Canal, Seawaymax ships are built for the locks of the St. Lawrence Seaway. They’re 740 feet long, 78 feet wide, and have a draft of 26 feet. The record load for one vessel is 28,502 tons. The Great Lakes are home to a number of larger ships that can carry bigger loads, but they can’t pass through the seaway.

The seaway’s peak year for cargo was 1979, when more than 7,300 vessels moved almost 75 million tons. Several factors have led to a long-term decline. European grain markets dried up. Canadian grain exports bound for Asia shifted to the West Coast. Competition from huge ocean ships and the Mississippi River system also have taken a toll. This year, battered by the global financial crisis in general and the depressed auto and steel industries in particular, the seaway expects its cargo to slip below 40 million tons.

Yet it would be wrong to conclude that the seaway is obsolete. Good infrastructure, supporting free trade is key to getting the world economy moving again. One recent study estimates that it saves the regional economy more than $1 billion in annual transportation costs. It also provides hydroelectric power–a critical role at a time when the world needs energy.

As the seaway ages, public officials will have to make sure the locks and canals have the resources they need to thrive–and guarantee that the St. Lawrence Seaway remains an indispensable unit of the global economy.

Tim Burrack raises corn and soybeans in partnership with his brother on their NE Iowa family farm. Tim is a Board Member of Truth About Trade and Technology