“Metropolis” (from the Greek word polis for “city”) means “a large city” and is not a city nickname peculiar to New York City. Philadelphia was called the “Metropolis of America” in the 1700s, but New York City assumed the ”(commerical) Metropolis of America” name in the 1800s.
 
When New York City’s borough became unified into Greater New York on January 1, 1898, a history titled The New Metropolis (1899) was written by E. Idell Zeisloft. Another book titled The New Metropolis: New York City, 1840-1857 (1981) was written by Edward K. Spann. “New Metropolis” was more a description of the newly emerging New York City than a formal nickname.
   
The Superman comics by DC Comics used a fictional city of “Metropolis” by 1939. Some have associated Superman‘s “Metropolis” with New York City, although Toronto and Los Angeles also have claims to this title.
   
 
(Oxford English Dictionary)
metropolis, n.
The chief town or city of a country (occas. of a province or district), esp. the one which is the seat of government; a capital. In extended use: any large, bustling city.
the metropolis (also the Metropolis) London, as contrasted with the whole of Britain, England, or the provinces; (occas.) London as a whole, as distinct from the City (see CITY n. 5a).
[a1398 J. TREVISA tr. Bartholomaeus Anglicus De Proprietatibus Rerum (BL Add.) f. 174, Asturia is a prouynce of e hider spayne..the citee hatte metropolis.]
1590 MARLOWE Tamburlaine Pt. 2 III. v. 36 That sweet land, whose braue Metropolis Reedified the faire Semyramis.
1636 W. DAVENANT Witts IV. i, O, to live here i’ th’ fair metropolis Of our great isle.
1667 DRYDEN Annus Mirabilis 1666 sig. A2 (heading) To the Metropolis of Great Britain, The most Renowned..City of London.
1692 L. ECHARD Gazetteer’s or Newsman’s Interpr. Pref., All the Metropolisses of Provinces.
1726 B. FRANKLIN Jrnl. in Wks. (1887) I. App. 104 Newport..is the metropolis of the island [sc. the Isle of Wight].
1807 R. SOUTHEY Lett. from Eng. (1814) I. 291 London is now so often visited, that the manners of the metropolis are to be found in every country gentleman’s house.
1807 R. SOUTHEY Lett. from Eng. (1814) II. 144 Penrith..seems here, by comparison, like a metropolis.
1862 P. M. IRVING Life & Lett. W. Irving (1864) I. i. 17 Kirkwall, the metropolis of the island group [sc. the Orkneys].
1892 Nation (N.Y.) 21 July 44/1 She [sc. Trinity College, Dublin] lives in a workaday world, because she lies at the heart of a metropolis.
1938 F. D. SHARPE Sharpe of Flying Squad ii. 30 These..cars poodle about the Metropolis well under 30 m.p.h.
 
Wikipedia: Metropolis (comics)
Metropolis is a fictional city that appears in comic books published by DC Comics, and is the home of Superman. Metropolis first appeared by name in Action Comics #16, in 1939.
 
Metropolis is depicted as a major US city on the country’s East Coast. The city is known for being one of the largest and wealthiest cities on earth. The co-creator and original artist of Superman, Joe Shuster, modeled the Metropolis skyline after Toronto, where he was born and lived until he was ten. Since then, Metropolis has become a city inspired by New York City.

Location
Like many of DC’s other fictional cities, the location of Metropolis has varied greatly over the years. Metropolis, however, is usually portrayed as a major city on the East Coast of the United States.
 
It has been said that, metaphorically, Metropolis is New York during the day, and Gotham City (home to Batman) is New York at night. This comparison is usually attributed to Frank Miller and is helped by the fact that Batman’s adventures are more often nocturnal than those of Superman; hence the “bat” symbolism. (Gotham is an old nickname for New York City, popularized by Washington Irving.) In terms of atmosphere, Batman writer and editor Dennis O’Neil has said that, figuratively, “Batman’s Gotham City is Manhattan below Fourteenth Street at eleven minutes past midnight on the coldest night in November.” However, New York City does exist as a separate city from Metropolis and Gotham City within the DC Comics universe; the Justice Society of America, for example, is based in New York as was the Teen Titans.
 
In a fictional Superman story set in the future (the 21st century), Metropolis is the literal merging of the Northeast Corridor of cities ranging from Washington, D.C. through New York City to Boston, to form a megalopolis.
 
In the 1940s Superman cartoons produced by Paramount Pictures and Fleischer Studios, Superman is said to live in New York rather than Metropolis, due to a reference in the cartoon “Electric Earthquake.” A Native American mad scientist claims that his people are the rightful owner of Manhattan, thus placing these cartoons in New York City.
 
Superman creator Joe Shuster grew up in Toronto and co-creator Jerry Siegel grew up in Ohio and worked in Cleveland. Originally intending to sell the Superman strips to a local newspaper, they set the stories there as well, and when the strips were re-used for the comicbooks, they changed the location to Metropolis. Action Comics #2, however, mistakenly portrays Clark Kent as a reporter for the Cleveland Evening News, although Metropolis is based on Toronto, Ontario (see Superman co-creator has humble Canadian roots).
 
In a 1970s edition of “Ask the Answer Man,” a column that ran occasionally in DC publications, it was stated that Metropolis and Gotham City were adjacent to New York City, across the harbor from each other. That same column stated that Star City (the home of Green Arrow) was in Connecticut, Flash’s Central City was in Ohio, and Hawkman’s Midway City was in Michigan. However, DC’s fanzine, Amazing World of DC Comics, number 14 (March, 1977), clearly stated Metropolis was located in Delaware, while Gotham was placed in New Jersey. A role playing game DC Universe atlas guide published by Mayfair Games also claimed that Metropolis was in Delaware.
 
In pp.223-225 of his 1978 work, The Great Superman Book, which is an encyclopedia of the first 40 years of the Superman comics, author Michael Fleisher cites many, many examples which demonstrate that Metropolis equates to New York City. The most blatant of these might be the statement he cites from Action Comics # 143, April, 1950, which states that the Statue of Liberty stands in “Metropolis Harbor”. The Statue of Liberty, in fact, stands in New York Harbor.
 
The 2005 comic Countdown to Infinite Crisis places Metropolis in the state of New York.
 
In relation to Gotham City
Metropolis is frequently depicted as being within driving distance of Gotham City, home of Batman. Like Metropolis, Gotham’s location has never been definitely established; however, it is usually treated as also being a major east coast city. The distance between the two cities has varied greatly over the years, ranging from being hundreds of miles apart to Gotham and Metropolis being twin cities on opposite sides of a large bay. In the Seven Soldiers of Victory series Klarion the Witch Boy, New York City is called the “Cinderella City”, referring to nearby Metropolis and Gotham as its “ugly step-sisters.” The film Superman Returns mentions Gotham City, as does Batman in an episode of the Justice League TV series. Bruce Wayne mentions the city of Metropolis in Batman Forever. In Superman: The Animated Series, Clark Kent’s mother Martha Kent refers to Batman as “that nut in Gotham City”.
 
The differences between Metropolis and Gotham City are almost as diverse as the differences between their respected superheroes. In contrast to the dark, gritty, and raw way Gotham City has been portrayed, Metropolis has almost always been depicted as a cleaner, warmer, and wealthier city.
(...)
History
The founding of Metropolis mimics that of New York City in the way that Swedish settlers bought it as a bargain from some natives on New Troy Island. The island was exchanged for a few trinkets.
 
Parallels to New York
The 2000 issue “Superman: Y2K” details much of the history of Lex Luthor’s family, which is bound up closely with Metropolis. In this issue, Metropolis is shown to have been founded by Pilgrims. One of Luthor’s ancestors was in the colony—and another was a Native American chieftain who was poised to wipe out the colonists before they could get settled. Before the attack, however, the colony erupted in fire (presumably, a meteor crashed and/or exploded over the settlement, setting most of the buildings ablaze. “Chief Luthor” and his tribe took pity on the colonists and offered the hands of friendship.
 
In the late 1800s, again mirroring New York City, Metropolis is shown to have been the scene of intense ethnic riots. Still later, on the eve of WWI, Lex Luthor’s grandfather (or great-grandfather) is shown to own large steel mills in the city. Metropolis, like most of the major cities in the U.S., was not spared the ravages of the Great Depression. Some of the more impoverished areas of the city, such as Suicide Slum, still bear the legacy of that time.
 
Around 2000, the city was given a futuristic makeover by the time-traveling Brainiac 13, a villainous descendant of Superman foe Brainiac. The transformation of Metropolis was covered in greater depth by the 2003 miniseries Superman: Metropolis. The city has since reverted to its former state.

More evidence that Metropolis mirrors New York is its geographic location across a river from the real life Jersey City as evident in Superman Returns. During the scene where the Daily Planet globe falls to the earth due to Lex Luthor’s earthquake the skyline of Jersey City is visible in the background, notably including the Goldman Sachs Tower and other nearby landmarks.
 
(OCLC WorldCat record)
Title: The new metropolis;
1600-memorable events of three centuries-1900; from the island Mana-hat-tan to Greater New York at the close of the nineteenth century,
Author(s): Zeisloft, E. Idell,  ed.
Publication: New York, D. Appleton and company
Year: 1899
Description: 2 p. l., iii-xxii, 639, [32] p. incl. illus., plates, ports., maps, plans, plates (part double, part col.) 29 x 37 cm.
Language: English
Note(s): “Autograph memorial edition deluxe limited to two hundred and fifty copies. Copy no. lxxxix [89]. Printed for Walter D. Munson.”
Class Descriptors: LC: F128.3
Responsibility: ed. by E. Idell Zeisloft
 
Amazon.com
The New Metropolis (Paperback)
by Edward K. Spann (Author)
Book Description
In one generation, New York was transformed into one of the great cities of the modern world. The causes and results of this change are emphasized by Edward K. Spann in The New Metropolis. This book is a brilliant evocation of the years when a seaport town was lost and a great metropolis gained. It is the happy story of American ingenuity, achievement, and urban success, but it is also the story of urban wretchedness and failure. Above all, it is the drama of a major city and its confrontation with the problems and opportunities of a modernizing world.
Product Details
Paperback: 546 pages
Publisher: Columbia University Press (October 15, 1981)
 
Amazon.com
The Monied Metropolis: New York City and the Consolidation of the American Bourgeoisie, 1850-1896 (Hardcover)
by Sven Beck
Product Details
Hardcover: 512 pages
Publisher: Cambridge University Press; New Ed edition (February 3, 2003) ert (Author) “