Welcome to Maine. Or is this still N.H.?

Most folks driving north on I-95 in New Hampshire are unaware of the exact moment they cross the border and enter Maine.

Does it happen at the center of the bridge spanning the Piscataqua River, or later, as they pass over the waterway's north shoreline?

It is a question that seems simple enough, yet the exact location of the border has been in dispute since the reign of King George II of England in the 1700s.

But perhaps not much longer.

Today, the Colonial-era legal imbroglio arrives at the US Supreme Court, where the justices will consider settling the issue once and for all.

The case involves much more than just an esoteric exercise in map reading and interpretation of royal decrees. At stake are millions of dollars in income-tax revenues Maine is collecting from more than 1,300 New Hampshire residents working at the Portsmouth Naval Shipyard.

The shipyard, where US nuclear submarines are built and overhauled, is located in disputed territory in Portsmouth Harbor, on an island within a stone's throw of Kittery, Maine.

Location is everything. If the shipyard is in New Hampshire, Maine's income tax is void. If it is in Maine, it applies. Victor Bourre has spent the past 15 years combing through dusty deed books and historical tomes searching for clear evidence that the shipyard is in New Hampshire.

"I felt so strongly about it that I have basically put my whole life into this thing," says Mr. Bourre, a former shipyard worker who lives in New Hampshire and for 10 years refused to pay any Maine income tax. "I consider what Maine is doing as an illegal use of power."

So, apparently, does the New Hampshire Attorney General's Office, which reviewed Bourre's findings and filed a petition with the Supreme Court.

Maine counters that the issue has already been conclusively resolved - twice. The first resolution came in 1740, when George II issued a decree that Maine says places the border in the middle of both the river and harbor, with the shipyard clearly on the Maine side of the waterway.

The second resolution came in 1976, according to lawyers for Maine, when the Supreme Court endorsed a negotiated end to the so-called "lobster wars" between lobstermen from the neighboring states. In that case, Maine and New Hampshire used the same 1740 decree to establish the ocean boundary between the two states.

Maine says New Hampshire's endorsement of the ocean boundary means that the state must also accept a middle-of-the-river interpretation of the 1740 decree as it applies to the harbor and river.

New Hampshire disagrees. The 1976 agreement only applies to the offshore border, state officials say. The rest of the 1740 decree remains in dispute, they say.

The decree says in part: "The dividing line shall pass up thro' the mouth of the Piscataqua Harbour & up the middle of the river into ye River of Newichwannock [part of which is now called Salmon Falls] & thro' the middle of the same to the furthest head thereof."

Prior to reaching the merits of the case, the justices must first decide whether prior legal action in the matter precludes any further involvement by the high court in the border dispute.

If the justices rule they have the authority to hear the case, they would appoint a fact-finder, or special master, to investigate the claims of both sides and establish a factual record. Then, the court could schedule oral arguments and begin considering the location of the border.

Bourre says he's found plenty of new evidence favoring New Hampshire.

It includes a 1763 map of the river and harbor prepared for officials in the then-territory of Maine that places the border along the northern shore of the harbor. In addition, he's located a decree by King George III in 1770 approving the creation of the first five counties in New Hampshire. The description of the newly created Rockingham County says it begins at the mouth of the river and includes the river, which Bourre says places the border on the northern shore of the harbor.

According to Bourre, the jurisdiction question became blurred in 1794, when a father sold his son one of the islands in the northern part of the harbor and recorded the deed in Maine. When the son later sold the island to someone else, that deed, too, was recorded in Maine. And then in 1800, when the island was purchased by the US government for the shipyard, the deed again was recorded in Maine.

Lawyers for Maine say they are not impressed by Bourre's findings. "New Hampshire's recently manufactured historical hypothesis is contradicted by undisputed historical fact," says Deputy Attorney General Paul Stern in his brief to the court. "In 1794, the Massachusetts General Court [which had jurisdiction before Maine became a state] ordered all towns to survey their boundaries and produce a map thereof. Kittery did so and included in its official map the shipyard islands," he says.

Mr. Stern also answers arguments that the name Portsmouth Naval Shipyard might suggest the legal jurisdiction of Portsmouth, N.H.

"Naval shipyards are not always named after the town in which they are located," he says.

(c) Copyright 2001. The Christian Science Monitor