We often refer to our highways, roads and avenues as “arteries,” as if they carried corpuscles instead of cars, platelets rather than pedestrians. But they are a city’s circulatory system, from the tiniest cul-de-sac capillary to the mightiest aortic interstate.

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       And that makes John DeFerrari and Douglas Peter Sefton veritable cardiologists of the asphalt. They are the authors of the new book “Sixteenth Street NW: Washington, D.C.’s Avenue of Ambitions.”

       Well, I say “asphalt,” but for a while, sections of 16th Street were covered in another material.

       “Washington went through this phase of being enamored with wood blocks,” DeFerrari said. Portions of 16th Street were paved with them.

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       “They learned their lesson pretty quickly on that,” DeFerrari said. “Definitely in a humid environment, wood doesn't hold up that long.”

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       Said Sefton: “They had a tendency to rot on you. It was like stepping on a soft cobblestone: not too good with a horse’s hoof.”

       But at first the real problem wasn’t what the road was made of, but the fact that it wasn’t made at all. Though 16th Street was on Pierre L’Enfant’s original design for the new capital — running north from the president’s house — the street was slow to grow.

       “Until nearly the end of the 19th century, Massachusetts Avenue was the upper limit of developed Washington,” DeFerrari said.

       The intersection of 16th Street with Massachusetts and Rhode Island avenues NW was “just a dusty crossroads,” said Sefton, notable mainly for the Louise Home, a Second Empire-style pile built in 1871 by banker William Wilson Corcoran as a refuge for Confederate widows. (Corcoran was a Confederate sympathizer whose wife and daughter — both named Louise — had died young.)

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       The topography and hydrology of the city made extending the street a difficult prospect. A creek called Slash Run paralleled the route before cutting east across it south of today’s Florida Avenue NW. This marshy and overgrown area became known as the Slashes, since the only way to traverse it was by slashing through the brush.

       The escarpment of Meridian Hill was also forbidding.

       “The next big obstacle is the valley of Piney Branch,” DeFerrari said.

       As in so much of the city, the Civil War spurred growth along 16th Street. Military encampments were established on Meridian Hill. As was common, African Americans fleeing the South moved to be near them. Meridian Hill had a vibrant Black community.

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       It also had stunning views of the city below, making it ripe for development at the busy hands of people like Mary Foote Henderson.

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       “She was like an imperial force,” Sefton said of Henderson who, with husband John B. Henderson, lived in a castle on the northwest corner of 16th and Florida NW. She had grand designs for 16th Street, many of which involved demolishing the modest homes of African American residents and replacing them with mansions and embassy buildings.

       “What Pennsylvania Avenue is is really what she wanted 16th Street to be,” DeFerrari said. “Of course, she wanted to rename it Avenue of the Presidents.”

       Henderson dreamed of lining the street with busts of every president and erecting on Meridian Hill a new Executive Mansion to replace the White House, which she saw as small and tattered.

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       Both authors have lived near 16th Street, traveling upon it countless times. DeFerrari grew up in Crestwood, the neighborhood between 16th Street and Rock Creek Park.

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       “We wrote a biography of the street,” he said. “It’s the story of the life of a street, from infancy to maturity.”

       It’s a life that’s been fairly stable — overwhelmingly residential, compared to, say, Connecticut Avenue or 14th Street NW — even if national and world events sometimes shape it. The two blocks nearest the White House have a new name: Black Lives Matter Plaza.

       Among the first things newcomers notice about 16th Street NW is the abundance of churches. Why are there so many?

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       “People often ask that,” DeFerrari said. “I wish I could say, ‘George Washington said 16th Street should be where the churches are.’ There isn’t anything like that.”

       It does have qualities that make it appealing to houses of worship. It's centrally located, thus easy for people to get to. It has the cachet of one of the city’s oldest and most prestigious churches: St. John’s, across from the White House.

       “There’s also the fact that the commercial prohibition means you’re going to be in a serene residential neighborhood and not have a liquor store next to you or an X-rated theater across the street,” DeFerrari said.

       Added Sefton: “You’re pretty far from sin.”