A city of a state that’s not very pleasant might be called the “armpit of the nation” or the “armpit of America.” Armpits smell.
 
“The midwest is the armpit of the nation” was cited in print in 1966 and “Hudson college, the armpit of America” was cited in 1970. The epithet has been used to describe many places.
 
New Jersey (or a particular town in New Jersey) has long been called an “armpit.” A 1974 Pennsylvania newspaper described graffiti on the Lower Trenton Bridge:
 
“As you cross the ‘Trenton Makes, The World Takes’ bridge, some ancient scribe painted on the underpass at the Trenton side of the bridge. ‘Welcome to the armpit of the nation.’”
 
   
(Oxford English Dictionary)
ˈarmˌpit, n.
fig. Used (esp. in the formula the armpit of the nation, etc.) to designate a place or part considered disgusting or contemptible; a place that ‘stinks’. colloq. (chiefly U.S.).
[1965   Amer. Speech 40 194   Pits, n. This is a slang abbreviation of the term armpits, again with an extension of meaning to entail the idea of body odor (‘He’s got the pits’) or, more broadly, something unpleasant (‘It [sc. the party] was really the pits’).]
1968–70   Current Slang (Univ. S. Dakota) III–IV. 3   Armpit of the nation, n. Las Cruces.—New Mexico State.
1973   N.Y. Times 19 Aug. 15   She is an amateur,..with no real notion of who might be out there in the armpit of America, grunting at what she says.
   
21 August 1966, Chicago (IL) Tribune, “So it’s a college you’re choosing!” by Gary Barger, pg. I13:
“The midwest is the armpit of the nation.” 
 
17 October 1969, Tyrone (PA) Daily Herald, “Letter To The Editor,” pg. 4, col. 4:
People of Tyrone—we are behind the times; we have been called the “armpit of the nation” long enough.
(Written by Robert FIsher, Tyrone, PA.—ed.)
 
8 February 1970, Chicago (IL) Tribune, “Quinn Has Doubts—Like His Characters” by Gene Siskel, pg. F1, col. 4:
“Hudson college, the armpit of America.”
(Written on a blackboard by an unknown student.—ed.)
 
8 May 1973, El Paso (NY) Herald-Post, “Ernie D. Okays Buffalo” by Peter Ciccarelli, pg. C3, col. 4:
Or as one veteran jock of the “Queen City” (Buffalo, NY—ed.) once called it, “The Armpit of America.”
 
11 August 1974, Bucks County Courier Times (Levittown, PA), “Graffiti” by Susan Sprague, Dimension magazine, pg. 1, col. 2:
As you cross the “Trenton Makes, The World Takes” bridge, some ancient scribe painted on the underpass at the Trenton side of the bridge. “Welcome to the armpit of the nation.”
 
3 May 1976, Sandusky (OH) Register, “Cavs Give Cleveland Transplant Cause For Joy” by Harry Lorber, pg. A-10, col. 1:
No longer will Cleveland be known as the armpit of the nation.
 
29 October 1979, Times-Standard (Eureka, CA), “American cities losing a tough fight” by Richard Reeves, pg. 4, col. 3:
“You have to live with the image that Baltimore is the armpit of America.” said a medical student whose family has lived there for nine generations
 
Google Books
Remaking Cities:
Proceedings of the 1988 International Conference in Pittsburgh
Edited by Barbara Davis
Pittsburgh, PA: Pittsburgh Chapter of the American Institute of Architects
1989
Pg. 8:
“It’s the armpit of the nation!” My friend said, “Have you ever been to Pittsburgh? It’s a beautiful city.”
 
23 July 1990, USA Today, “Sore points, state by state”:
PA.: Calls New Jersey ``armpit of the nation’’ because of stench-spewing factories and N.J.‘s geographical location
 
21 September 1995, Waunakee (WI) Tribune, “Richard Meyer: Eastern transplant loves life in the Midwest” by Willow Bacon, pg. 2, col. 1:
“My first 15 years in Bayonne, New Jersey were terrible,” he remarked. “It was like living in the armpit of America/”
 
New York (NY) Times
IN THE WILD;Ecotourism: Mixing Dollars and Environmental Sense
By ANDY NEWMAN
Published: May 26, 1996
(...)
Felicity Munn, a Montreal-based travel writer who took the state-sponsored tour, said she had found much to recommend: “There were so many spots where you’d want to stay at bed-and-breakfasts and hire a bicycle and ride around, and the canoeing was lovely.
 
“Before the trip,” she said, “I knew nothing about New Jersey except that it was the armpit of America. This really opened my eyes.”
     
Google Books
Putting the Children First:
The Changing Face of Newark’s Public Schools
Edited by Jonathan G. Silin and Carol Lippman
New York, NY: Teachers College Press
2003
Pg. IX:
However, we saved a special set of insults for people from one place— New Jersey—a place we called “the armpit of the nation.”
 
Google Books
Everyone Else’s Girl
By Megan Crane
New York, NY: Warner Books
2005
Pg. ?:
“Baby,” he said patiently, “New Jersey is the armpit of the nation. What do you expect?”
 
Google Books
Everyone Else’s Girl
By Megan Crane
New York, NY: Warner Books
2005
Pg. ?:
“Baby,” he said patiently, “New Jersey is the armpit of the nation. What do you expect?”
 
Google Books
Village of Tears
By Christopher Abbott
Victoria, BC: Trafford Publishing
2006
Pg. 41:
Catch was familiar with the less-than-kind references to New Jersey. He had heard it called the “armpit of the nation” and the “the country’s largest landfill.” But the serenity he found here was a world, no, a universe, apart from crowded cities like Newark, Elizabeth or Jersey City.
   
Urban Dictionary
armpit of the nation
the state of new jersey
ive just drove through the armpit of the nation
by Thrombeldinbar November 26, 2006  
 
Urban Dictionary
new jersey
(...)
New Joysee was the 41st state in the United States of America. The state slogan was “The Armpit of America!”, now “The Fabulous Armpit State!”. As of 10/01/07 the capitol is New Joysee City.
(...)
by Phayte January 01, 2007
   
NJ.com
Dove to N.J.: ‘When people call you ‘The Armpit of America,’ take it as a compliment’
By Alex Napoliello | NJ Advance Media for NJ.com
on February 28, 2014 at 11:07 AM, updated February 28, 2014 at 3:50 PM
A billboard promoting a new line of Dove deodorant has a message for New Jersey residents.
 
“Dear New Jersey, when people call you ‘The Armpit of America,’ take it as a compliment. Sincerely, Dove.”
 
That text sits alongside an image of a woman wearing a white tank top and raising an arm to display her armpit. The billboard is set to appear in July, according to The New York Times.
 
Daily News (New York, NY)
Dove pulls billboard calling New Jersey the ‘armpit of America’
New Jersey residents were up in arms about the planned deodorant billboard, which referred to the state as the ‘armpit of America.’ Dove insists the ad was meant to ‘call attention to the fact that armpits can and should be considered beautiful.’
BY VICTORIA TAYLOR   NEW YORK DAILY NEWS Wednesday, March 5, 2014, 1:04 PM
Dove has announced it will pull a billboard that encourages residents of the Garden State to embrace living in the “armpit of America” after New Jerseyans raised a stink.
 
“We did not wish to cause any misunderstanding and apologize for any offense,” the brand wrote on its Facebook page. “Our intent with the ‘Dear New Jersey’ billboard, which was one of many ads for our campaign, was to call attention to the fact that armpits can and should be considered beautiful and ask women everywhere to accept this as something that is okay.”
 
The proposed billboard said, “Dear New Jersey, When people call you ‘The Armpit of America,’ take it as a compliment. Sincerely, Dove.”