With just a brief glance around Beacon Hill, one can tell it is a neighborhood of deep historical significance. State and local politics have their seats of power here. Sites that mark milestones in the birth of the U.S. are intermingled with everyday life.

But the brownstone residential buildings that line Beacon Hill’s cobblestone streets bear a more subtle historical importance.

They tie into an early American architectural tradition, and they make the city of Boston its earliest participant.

“Brownstones” is the colloquial name for the three-to-five-story brick townhouses that fill Boston’s historic neighborhoods, like Beacon Hill and the Back Bay. Many brownstones were originally built in the 19th or early 20th centuries.

Most of the brownstone in these historic buildings came from the Portland Brownstone Quarries in Connecticut, which was designated a national historic site in 2000. Dr. Joanne Kleussendorf, the geologist who submitted the quarry for historic site consideration, wrote extensively about the historical significance of brownstone in American architecture.

“Utilized in many architectural styles over the span of nearly three centuries, brownstone was used to construct both the palatial mansions of the wealthy and rowhouses of the middle class,” Kleussendorf wrote in her submission. “Prior to the 1840s, brownstone was used mostly as building foundations, quoins, and trim. In the early 1840s, however, the Romantic movement in architecture swept the nation.”

Brownstone is a warm, earthy color and is easily carved into artful shapes, which made it a perfect fit for this movement, Kleussendorf wrote. And so, in the mid-1800s, the “Great Brownstone Era” began. Brownstone was quarried in Portland and shipped along the Connecticut River to major U.S. cities like New York, Philadelphia and Washington, D.C.

But, according to Kleussendorf, Boston was already ahead of the curve.

“Portland brownstone appears to have been shipped to Boston early on,” Kleussendorf’s submission states. “One of the earliest recorded uses of this stone was in the Old Province house there, which was erected in 1679 with a flight of twenty massive brownstone steps. Constructed between 1737 and 1740 on Beacon Hill in Boston, the Thomas Hancock house had Portland brownstone trim.”

The Old Province House, formerly the seat of Massachusetts royal governors, was situated on what is now Washington Street in Downtown Crossing, according to a historic marker placed there. The Thomas Hancock house, more commonly known as Hancock Manor, sat at 30 Beacon Street, on what is now the grounds of the Massachusetts State House.

The construction of those buildings predates the “Great Brownstone Era” by at least 100 years, which means that Boston was on the brownstone trend far ahead of any other city. So, despite their popularity in other areas of the country, brownstones in Boston carry special significance.

This is evident with just one look at Beacon Hill, where original brownstone houses still stand today. Consider the double townhouse on Beacon Street built by architect Asher Benjamin in 1808. One half of the double townhouse is a national historic site and museum. The other is refurbished and fully residential. Brownstones tie directly into the historic fabric of the city, which makes the winding streets of Beacon Hill even more special.