The Astrodome in Houston, Texas, was completed in 1965 and was dubbed the “Eighth Wonder of the World.” There are the Seven Wonders of the Ancient World. The Astrodome was called a “wonder of the world” in the New York (NY) Times on December 6, 1964, and “Houston Dome: The 8th Wonder” in Newsday (Long Island, NY) on January 26, 1965.
   
The Louisiana Superdome in New Orleans, opened in 1975, was called the “Ninth Wonder of the World.”
       
     
Wikipedia: Astrodome
The NRG Astrodome, also known as the Houston Astrodome or simply the Astrodome, is the world’s first multi-purpose, domed sports stadium, located in Houston, Texas. Construction on the stadium began in 1962, and it officially opened in 1965. It served as home to the Houston Astros of Major League Baseball (MLB) from its opening in 1965 until 1999, and the home to the Houston Oilers of the National Football League (NFL) from 1968 until 1996, and also the part-time home of the Houston Rockets of the National Basketball Association (NBA) from 1971 until 1975. Additionally, the Astrodome was the primary venue of the Houston Livestock Show and Rodeo from 1966 until 2002. When opened, it was named the Harris County Domed Stadium and was nicknamed the “Eighth Wonder of the World”.
 
Wikipedia: Seven Wonders of the Ancient World
The Seven Wonders of the World or the Seven Wonders of the Ancient World is a list of remarkable constructions of classical antiquity given by various authors in guidebooks or poems popular among ancient Hellenic tourists. Although the list, in its current form, did not stabilise until the Renaissance, the first such lists of seven wonders date from the 1st-2nd century BC.
       
6 December 1964, New York (NY) Times, “In Texas, Where Everything Is Big, Houston Stadium Is the Greatest,” pg. 2S, col. 3:
These were some of the superlatives that the Houston club delivered this week as it unveiled its new “wonder of the world” to visitors at the winter baseball meeting.
 
26 January 1965, Newsday (Long Island, NY), pg. 36C, col. 1 headline:
Houston Dome: The 8th Wonder
By Steve Jacobson
 
30 January 1965, Saturday Express and News (San Antonio, TC), “Don’t Quote Me” by Johnny Janes, pg. 1-C, col. 1:
After all, didn’t they create and build the Astrodome, which they modestly call the “eighth wonder of the world?”
 
9 February 1965, State-Times (Baton Rouge, LA), “Sports from the Press Box” by Dan Hardesty, pg. 2-C, col. 1:
A Wonder of the World
HOUSTON—“This is the eighth wonder of the world.”
 
“You mean there are seven other things in the world to compare with this?”
 
OCLC WorldCat record
Inside the Astrodome, eighth wonder of the world : stories, facts, figures and illustrations on Houston’s fabulous Astrodome.
Author: Houston Sports Association.
Publisher: [Houston, Tex] : [Houston Sports Association], [1965]
Edition/Format:   Print book : English
   
OCLC WorldCat record
Greetings from the eighth wonder of the world
Author: Al Reinhart
Publisher: 1975.
Edition/Format:   Print book : Biography : English
Subjects
Astrodome (Houston, Tex.)
Notes: Caption title.
In a whole issue of: Texas monthly. April 1975.
 
Twitter
8thWonderOfTheWorld
@The_Astrodome
Been going strong since 1965. Apparently, my days are numbered. Then again, they’ve been trying to get rid of me for a while now.
Houston, Texas
Joined April 2012
 
Twitter
Texas Humor
@TexasHumor
You might be a Texan if you know that the 8th wonder of the world was the Astrodome.
6:10 PM - 21 Jul 2014
     
OCLC WorldCat record
Remembering the astrodome, the eighth wonder of the world: Fifty years after its grand opening, the spectre of the Houston stadium still looms large
Author: Macgregor J.
Edition/Format: Article Article : English
Publication: Smithsonian, v2015 nApril (2015 01 01)
 
OCLC WorldCat record
The eighth wonder of the world : the life of Houston’s iconic Astrodome
Author: Robert C Trumpbour; Kenneth Womack
Publisher: Lincoln : University of Nebraska Press, [2016]
Edition/Format:   eBook : Document : State or province government publication : English
Summary:
When it opened in 1965, the Houston Astrodome, nicknamed the Eighth Wonder of the World, captured the attention of an entire nation, bringing pride to the city and enhancing its reputation nationwide. The Eighth Wonder of the World tears back the facade and details the Astrodome’s role in transforming Houston as a city while also chronicling the buildingi’s pivotal fifty years in existence