The oldest existing Jewish house of worship in North America, the Touro Synagogue, holds more than two centuries of history within its brick walls. George Washington visited here, and throngs of tourists include it on their itineraries.

But age has crept up on the building, dedicated in 1763. The walls are deteriorating with mold, white paint chips litter the ground, a brass chandelier is slowly corroding and a poor ventilation system can make the sanctuary uncomfortable.

So a massive restoration is underway, the first in decades, as part of a $10 million campaign that includes money to build visitor facilities. The synagogue has been temporarily closed and sheathed in a white covering; the restoration is expected to conclude in December.

"Two hundred and fifty years is great for the building to have lasted," said Michael Balaban, a former Hebrew school teacher and leader of the Touro Synagogue Foundation. "But if we don't start to act now, we certainly won't get another 250 years out of the building, let alone another 50."

The history of the synagogue starts with a group of Sephardic Jews who arrived in 1658 in Rhode Island -- a colony founded by Roger Williams and his followers on the principle of religious tolerance. They established a congregation, and the synagogue was built a century later, designed by Newport architect Peter Harrison, whose other notable buildings include King's Chapel in Boston.

Washington visited in 1781 and later delivered a written proclamation guaranteeing that bigotry would not be tolerated in the new nation.

Two centuries later, President John F. Kennedy attended services there and called Touro "not only the oldest synagogue in America, but also one of the oldest symbols of liberty." President Dwight D. Eisenhower also attended services at Touro, as did poet Robert Frost.

Because of the conservation work, the congregation has been meeting in a chapel across the street since early May.

Meanwhile, workers will recoat the exterior brick walls after using a chemical stripper to remove 22 layers of paint. Modern wiring and new ventilation and sprinkler systems will be installed. The interior cloth wall covering will be removed to allow workers to get to mold underneath.

Construction of a two-building visitor center will begin after the conservation work ends. It will include exhibits on colonial Jewish history, the birth of religious freedom in America and a portrait gallery focused on distinguished Colonial-era Jews, among other features.

Organizers so far have raised roughly $8.5 million of the $10 million they are seeking.