By MARK SHERMAN and MATT VOLZ
WASHINGTON (AP) -- A Supreme Court dominated by Easterners tried to make sense Wednesday of a Western water dispute.
The court heard arguments in a lawsuit between a power company and the state of Montana over who owns the riverbeds beneath 10 dams sitting on three Montana rivers.
The state says it's owed more than $50 million in back rent and interest from the company, PPL Montana.
For an answer, the court is looking back as far as the travels of Lewis and Clark more than 200 years ago.
The outcome could affect property rights, public access and wildlife management along Montana's rivers, as well as those in other states.
The power company is appealing a Montana Supreme Court ruling that the state owns the submerged land beneath the dams. The decision turned in large part on that court's findings that the three rivers were navigable when Montana became a state, despite the presence of significant waterfalls on two of the waterways.
The justices were dealing with unfamiliar issues in an area without much in the way of prior decisions to guide them.
Justice Samuel Alito, from Trenton, N.J., repeatedly asked where to turn for help.
"I'm not a sailor," said Bronx-born Justice Sonia Sotomayor, explaining that she's not especially conversant in nautical terminology.
Sotomayor was trying to figure out whether it matters in deciding on navigability how far someone has to go to get around a waterfall.
Both PPL and Montana reference the journals of Meriwether Lewis and William Clark, whose expedition carried their supplies 17 miles around the Great Falls of the Missouri River in 1805.
Paul Clement, representing PPL, tried to offer a helpful comparison.
"For the New Yorkers, the East River is 16 miles long, the whole river," he said. Four justices come from New York City.
Gregory Garre, arguing for the state, said the temporary interruptions to travel by water do not mean that the river is not navigable for business purposes.
He then quoted Lewis' description of the Missouri River. Lewis, Garre said, didn't "think the world could furnish a finer example of a navigable river."
Justice Anthony Kennedy, one of two native Californians on the court said, "Did he write that during his 32-day portage?"
Better still, replied Garre, he wrote it after the arduous trip.
Seven history professors are backing PPL by saying the Missouri above the falls was not a useful channel of commerce.
But historian Stephenie Ambrose Tubbs, whose father, Stephen Ambrose, wrote an account of the Lewis and Clark expedition called "Undaunted Courage," says there is no question the river was used for commerce even before the expedition.
The titles to riverbeds beneath commercially navigable waterways go to state governments upon statehood. Non-navigable riverbed ownership stays with the federal government.
Montana claims that the title to all the land under the Missouri, Clark Fork and Madison rivers within its border transferred when it became a state in 1889. When deciding navigability, the entire river should be considered, not just segments, and a portage around a natural obstruction does not interrupt the flow of those rivers as a highway of commerce, the state says.
PPL argues that eight of the 10 dams in question are built on non-navigable portions of Missouri and Clark Fork rivers -- the Great Falls of the Missouri and Thompson Falls on the Clark Fork -- and therefore the title to the lands under those dams should not go to the state.
The fact that Lewis and Clark had to get out of their boats and spend weeks carrying their supplies around the falls proves that portion of the river is non-navigable and should not fall under state title, the company said.
Backing the power company's argument are seven history professors led by David Emmons of the University of Montana, whom PPL hired as an expert witness.
The professors say the upper Missouri River above the Great Falls was not a useful channel of commerce. Lewis and Clark's description of the Missouri did not mean the river was commercially navigable, argued the professors led by University of Montana's David Emmons.
The power company said the state has never made a similar title claim over the past 100 years that many of the dams have existed.
The company's argument is backed by the Justice Department, livestock associations, farm bureaus and corporations that say giving the state that previously uncontested title to the submerged lands could disrupt property rights across the nation.
"If Montana's action is allowed to stand, other states will surely follow suit with their own judicial takings," PPL wrote in its brief to the court
Twenty-six states and numerous conservation groups are backing the state, saying a decision in favor of PPL would create a patchwork segmentation to the title to the beds of navigable rivers.
A decision is expected by June.
The case is PPL Montana v. Montana, 10-218.
Volz reported from Helena, Mont.
Copyright 2011 The Associated Press.