Maine and New Hampshire have agreed on the need to replace Memorial Bridge, the smallest of three spans at Portsmouth Harbor. It’s a decision that is likely to pay economic dividends for generations to come.

The fate of Memorial Bridge was in serious doubt until last week because of faint support from Gov. John Baldacci. The need for action became more apparent in July, when a large piece of metal fell from the  bridge, nearly striking a tour boat passing underneath.

Maine’s governor gave the project his full backing last week, saying, “It’s clear to me that we must replace the Memorial Bridge.”

He made the remark as the two states agreed last Friday to establish a task force to seek up to $300 million to fund work on all three Piscataqua River bridges. And on Tuesday, Baldacci and New Hampshire governor John Lynch signed the executive order that will get planning underway for replacement of that antique lift-span bridge at Badgers Island.

Built in the 1920s, Memorial Bridge connects the downtowns of Kittery and Portsmouth, N.H. The two communities engage in brisk commerce, and Maine’s Department of Transportation recently spent $5 million upgrading the approach to the bridge from the  Kittery Traffic Circle. It provides the only pedestrian and bicycle crossing of the Piscataqua River, and is also a major access route for Portsmouth Naval Shipyard workers arriving from New Hampshire.

By acknowledging that the  bridge must be replaced and authorizing the formation of a task force, Baldacci has strengthened a partnership with New Hampshire that makes success much more likely.

The  task force’s responsibilities also extend to the Sarah Mildred Long Bridge, the middle span carrying the Route 1 Bypass, and the high-level bridge that carries I-95 traffic into and out of Maine.

But Memorial Bridge is the span that requires immediate attention. Replacing it will ensure that the roads connecting two downtown districts will not become dead ends.