New York Islanders-New York Rangers is one of the most vociferous rivalries in American professional sports. AP Photo/Kathy Willens

On one side of the East River, the New York Rangers are currently the hottest team in the National Hockey League, having won six straight games.

On the other side, the New York Islanders sit just three points behind the final playoff spot, having experienced a recent resurgence.

This is the current state of professional hockey in New York City and it will be on full display tonight when the Islanders play host to the Rangers in what could shape up to be the best hockey game in the Metropolitan Area this season.

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The “Battle of New York” has long been one of the greatest rivalries in American sports history ever since the Islanders first played the Rangers in an exhibition match on Sept. 27, 1972 at the Nassau Coliseum in Uniondale, N.Y.

In few other rivalries have two teams competed not only in the same market, but also in the same division, playing at least four times a season.

Other intra-city New York rivalries like Mets-Yankees and Jets-Giants do not have the same flair since they play in different conferences. The Nets and Knicks have only met three times in the playoffs, compared to the eight playoffs battles between the Rangers and Islanders.

“Islanders fans and Rangers fans mix regularly — too regularly, if you were to ask most of them,” authors Stan Fischler and Zachary Weinstock write in their book “Rangers vs. Islanders.” “They split arenas when their beloved teams face off and split communities, workplaces, worship-places and even families in between.

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“Which is why, unlike every other supposed rivalry in America, this one has not waned, and will not ever, and has proven as such many times.”

Islanders vs. Rangers games have always been competitive, but the Isles’ recent move to Brooklyn last season has given a whole new meaning to the rivalry.

What were once Rangers fans versus Islanders fans, city slickers versus suburban folks, now pits Brooklynites against Manhattanites as well.

“There has been a very smooth segue from Rangers vs. Islanders at Nassau [Coliseum] to Rangers vs. Islanders in Brooklyn and it has that added flavor,” Fischler told the Brooklyn Eagle. “The Brooklyn brand is a special brand. It’s a brand that became a brand because there’s a thing called Brooklyn spirit.

“There’s something special about the Brooklyn spirit. So you add that little more pizzazz, that little more mustard to the whole rivalry and its even better.”

Ahead of tonight’s match, it’s important to remember how Rangers vs. Islanders turned into one of the most vociferous rivalries in sports history and to look back at its original Brooklyn roots.

Brooklyn’s First Hockey Team

What people might forget, and what some younger fans may not even know, is that the original Islanders-Rangers rivalry started as far back as the 1920s between the Rangers and the New York Americans.

“One could say that the Americans were the earlier Islanders, but with a different name,” wrote Fischler and Weinstock.

According to “Rangers vs. Islanders,” the Americans were owned by a bootlegger named “Big Bill” Dwyer who relocated a team from Ontario, Canada to Madison Square Garden (MSG) in April 1925.

While the Americans were the first team in New York City, they were soon eclipsed when promoter Tex Rickard and MSG President Colonel John Hammond brought in the Rangers.

“On the ice, a bitter Americans-Rangers rivalry was cultivated without need of even one spirited game or fight,” wrote Fischler and Weinstock. “The awkward business relationship between the teams provided more than enough animosity.”

Despite the team’s struggles on the ice, “their fans continued to root them on, just as Brooklyn’s ‘Faithful’ supported the Dodgers,” wrote the two authors. “‘We had fans mostly from Brooklyn,’ said [then-coach Mervyn] Dutton, ‘while the Rangers had the hotsy-totsy ones from New York.’”

At the start of the 1941-1942 season, Dutton changed the team’s name to the Brooklyn Americans to emulate the fierce baseball rivalry that existed between the New York Giants at Manhattan’s Polo Grounds and the Brooklyn Dodgers at Ebbets Field in Flatbush.

“Fed up with the second-class treatment accorded his team at the Garden, Dutton had decided as early as 1939 to build a new arena in Brooklyn,” wrote Fischler and Weinstock. “In the meantime, Dutton moved his team’s practices to the ancient Brooklyn Ice Palace on Atlantic Avenue between Nostrand and Bedford avenues in the Bedford-Stuyvesant community of Kings County.

“Dutton and his wife Phyllis, as well as several of his players, moved to Flatbush, and even the traditional star-spangled uniform gave way to new colors and a sweater with the letters B-R-O-O-K-L-Y-N running from right to left diagonally down the jersey.”

In 1942, however, Dutton’s dream of bringing a team to the corners of Flatbush and Atlantic avenues (sound familiar?) was abandoned, and the team folded due to World War II and the team’s long-standing financial troubles.

To Dutton’s knowledge, there would never be hockey played in our fair borough.

A Team Grows in Brooklyn

Fast forward to Oct. 24, 2012, the Islanders and Barclays Center mutually agree that the team will be moving from the Nassau Coliseum to Barclays Center, home of the Brooklyn Nets.

When the team officially moved to Manhattan’s gritty neighbor at the start of the 2015-2016 season — 74 years after the introduction of the Brooklyn Americans — the “Battle of New York” was now being coined the “Subway Series.”

“Ironically, this was the precise location that the Americans’ boss Red Dutton had earmarked for his proposed Amerks home during the 1941–42 season,” wrote Fischler and Weinstock. “Instead of dissolving, the most intense rivalry in hockey was actually about to get closer, by a matter of 25 miles!

“It would be Brooklyn against Manhattan, just as Dutton once hoped it would be.”

The Islanders’ move to Brooklyn meant that hockey fans and hipsters would have to coexist.

The team, however, embraced the borough, removing the Long Island silhouette from the team’s logo and introducing an alternative black and white jersey reminiscent of the Nets attire.

“The Dutton dream came true, except that the only thing about his beloved Americans in Brooklyn in the fall of 2015 was a magnificent exhibit at the Brooklyn Historical Society (BHS), aptly titled “BROOKLYN AMERICANS,” stated Fischler and Weinstock in their book.

The Eagle attended the opening of the show where a relative of Dutton named Bill Dutton was on hand.

As Bill “shmoozed the crowd, the more the standing-room-only audience got the feeling that the contemporary Islanders were simply Dutton’s Americans reincarnated,” Fischler and Weinstock revealed.

The Islanders’ first season in Brooklyn was labeled a resounding success as the team won its first playoffs series in 23 years and swept the Rangers in a season series for the first time ever.

“Back in 1945, Madison Square Garden brass nervously squashed the idea of a rival team in Downtown Brooklyn,” wrote Fischler and Weinstock. “When it finally happened, the city embraced it head-on. In a sense, nothing could be more appropriate than the contemporary version of the Brooklyn-Manhattan hockey rivalry.

“Really, the only difference is that instead of the Amerks battling the Blueshirts, it’s Brooklynites versus Manhattanites, and this rivalry threatens to go on forever.”

Game on!

ABOVE: From left: Hockey analyst Stan Fischler; Bill Dutton, nephew of Red Dutton and co-owner of the Arizona Coyotes; Co-owner of the Islanders Jon Ledecky; Brooklyn Historical Society President Deborah Schwartz; Steven M. Cohen; Brooklyn Historical Society Vice President Marcia Ely; and Lisa Cohen. Eagle file photo by Rob Abruzzese