Graphic from the Sears Holdings Corporation

Sears, Roebuck & Company was acquired by Kmart Holdings (formerly the Kmart Corporation) in March 2005. The merged companies were placed under a new corporate heading known as Sears Holdings. However, stores continued to operate under the original Sears and Kmart banners. After years of declining sales (and some serial asset stripping), Sears Holdings filed for Chapter 11 bankruptcy in October 2018.

A new company, TransformCo Properties, was formed in February 2019. They acquired assets of Sears Holdings and began to shrink operations. 223 full-line Sears stores were maintained...at least for the time being. Meanwhile, all stores in the Canadian Sears division had been shuttered by January 2018. As of September 2024, there were just ten operational, full-line Sears stores in the United States and Puerto Rico. Three stores were still in operation in Guatemala and El Salvadore, with ninety-two Sears stores in Mexico being owned by another company.

Between November 1999 and February 2014, Sears' largest store was located in Canada's TORONTO EATON CENTRE. It enveloped 817,800 square feet (Note: the Canadian Simpsons-Sears co-branding had been retired in 1973).
Photo from Wikipedia / "Nephron"

 

Following the demise of the EATON CENTRE Sears, keeping track of which store was largest became a challenge. Sears was closing stores at a rapid rate. Apparently, Southern California's SOUTH COAST PLAZA Sears (with 295,200 square feet*) was the largest between 2014 and 2019. Sears at Chicagoland's WOODFIELD MALL (with 264,000 square feet*) was largest between 2019 and 2021. With the shuttering of that store, the PLAZA LAS AMERICAS Sears, in San Juan, Puerto Rico, assumed the title. It covers 243,200 square feet*.  
Graphic from Sears Holdings Corporation 

Graphic from the J.C. Penney Company

J.C. Penney's first foray outside the continental United States was in Alaska, where an Anchorage store opened in 1963. Operations were expanded to Hawaii (1966), Puerto Rico (1968), Belgium (1969) and Italy (1971). 

South of the border stores were operated, in Mexico and Chile, between 1995 and 1999. A Brazilian division was established with the acquisition of Lojas Renner, in 1998. Operations outside of the "Lower 48" were curtailed in 2003, with one Alaska store, and five in Puerto Rico, remaining in business.

J.C. Penney filed a Chapter 11 bankruptcy in May 2020 and emerged from proceedings in November. A joint venture of the Simon Property Group and Brookfield Property Partners acquired the Penney Company. In September 2024, there were 660 operational brick and mortar stores.  

The J.C. Penney at San Juan's PLAZA LAS AMERICAS is that chain's largest store. Encompassing 4 levels and 300,700 square feet, it opened in April 1998, replacing a circa-1968 store.
Photo from www.plazalasamericas.com

 

* The square footage of the three Sears stores mentioned does include the size of their freestanding Auto Centers.

For more in-depth histories of America's Big Three merchandisers, follow these links...

http://www.company-histories.com/Montgomery-Ward-Co-Incorporated-Company-History.html

http://www.company-histories.com/Sears-Roebuck-and-Co-Company-History.html

http://www.company-histories.com/JC-Penney-Company-Inc-Company-History.html

Sources:

The New York Times
The Chicago Tribune
http://www.kshs.org
http://pleasantfamilyshopping.blogspot.com
"Earl Corder Sams & The Rise Of J.C. Penney" - Davis Delbert Kruger
http://plma.com (History of Private Labels)
http://www.company-histories.com/Montgomery-Ward-Co-Incorporated-Company-History.html
http://www.company-histories.com/Sears-Roebuck-and-Co-Company-History.html
http://www.company-histories.com/JC-Penney-Company-Inc-Company-History.html
http://www.chsmedia.org (Montgomery Ward & Company Records, 1872-2000 / Jane McCarthy)
https://www.historicvehicle.org
http://searsmotorbuggy.com / John M. Daily
http://searsarchives.com
http://www.whirlpoolcorp.com
Kiplinger's Personal Finance - November 1965
http://www.businesswire.com
http://mds.marshall.edu  / Retail Internationalization JC Penney’s Global Expansion

https://www.forbes.com / Michael Lisicky

https://www.creativebloq.com

https://christmas.musetechnical.com / Catalogs & Wishbooks

"Montgomery Ward" article on Wikipedia
"Sears" article on Wikipedia
"J.C. Penney" article on Wikipedia