This week's bridge (even though it's a couple weeks late) is the last bridge I will be covering over the Bronx River - the Boston Road Bridge.
This bridge is not to be confused with the bridge farther north up Boston Road, over the Hutchinson River, which is called the Eastchester Bridge. This bridge is just south of the Pelham Parkway intersection, and west of the Bronx River Parkway, at the eastern entrance of the Bronx Zoo. Zoogoers must cross the bridge on foot to enter the zoo from the parking lot. Boston Road itself, in fact, has restricted vehicular access here and through the zoo, before regular public access resumes at E. 180th St. But you can very easily run, or walk here from Bronx Park East and the Pelham Parkway (very near the elevated subway station for the 2 and 5 trains). But as it's the entrance to the zoo, there are a lot of pedestrians, and it leads only to the zoo entrance, so not really a great running bridge. But it is near Bronx Park, which has a beautiful greenway north of Pelham Parkway, and Pelham Parkway, which has a nice greenway as well.
The bridge itself is a basic concrete bridge, I don't have the numbers on it, but you can get an idea of its length and appearance from the pictures above. One source lists it as being built in 1920, which sounds good to me. I'll mention here as well that Boston Road, called Boston Post Road north of the NYC line, was obviously so named because it was a road built in the 1700's to carry mail to and from Boston.
As I mentioned, this is the last bridge over the Bronx River that I will write about. However, according to Google Maps there are two other bridges over the river in the New York Botanical Garden, whic carry a roadway, named Bronx Park Road, over the river twice as it loops through the park. But the Botanical Garden charges admission, and since this is meant for runners' information, and runners are unlikely to pay to go into a park to do their run (and in fact I admit I've never been into the Botanical Garden), I won't be writing about those two bridges.
And also since this is the last time I'll mention the Bronx River, it's a good time to give a little trivia note. It's well-known that the name Bronx comes from Jonas Bronck, a Swedish-born Dutch settler who established a farm near the river in 1639. When he died in 1643 the river, named Aquehung, or "River of High Bluffs," by the Mohegan, became known as Bronck's River (later Bronx River). But the name Bronx was not associated with any area of land for centuries. The villages in what is now The Bronx all had their own names and were part of Westchester County until 1874 when New York City (just Manhattan at the time) annexed the villages west of the Bronx River, but it was all still named simply New York City, and New York County. In 1895 the city annexed the rest of what is now the Bronx, but it was still just called New York City, and New York County, until 1898 and the consolidation of Greater New York - the annexation of Queens, Kings and Richmond Counties, which became the boroughs of Queens, Brooklyn and Staten Island. Only then did the northern borough receive its name, after the river that runs through it. (And it was only in 1914 that the borough achieved separate county status from New York County, and became Bronx County.) All that is a long way of saying that the borough was named after the river, more than actually after Mr. Bronck himself.
Sorry, one more trivia note about the river: it is the only true river in New York City, and not a tidal body of water. So there.