1397-1400, 3432 UNITED STATES (Illinois) - Chicago Skyscrapers

3432 Chicago skyline dominated by John Hancock Center

In the 1770s, Jean Baptiste Point du Sable established a fur trading post in the area which later became known as Fort Dearborn, along the bank of the Chicago River. In 1837, the settlement had a little more than 3,500 inhabitants and was incorporated as a city. Located near a portage between the Great Lakes and the  Mississippi River watershed, Chicago emerged as an important transportation hub between the eastern and western United States, becoming the fastest growing city in the world for several decades. 

1397 Downtown Chicago with Northwestern Train Station,
Presidential Towers and Willis Tower

After the Civil War ended in 1865, the American economy was transformed by the industrial revolution, in which the city of Chicago was its leader, becoming America's second largest city and a leading industrial center. The Great Chicago Fire, which destroyed most buildings within the downtown area, led to the largest building boom in the history of the nation. In 1885, the first steel-framed high-rise building, the Home Insurance Building, rose in the city as Chicago ushered in the skyscraper era.

1397 Chicago skyline seen from the Chicago River

Moreover, the city gave its name to the Chicago School and was home to the Prairie School, two movements in architecture, being able to say that the architecture of Chicago has influenced and reflected the history of American architecture. Numerous architects have constructed landmark buildings of varying styles in city. Some of these are the so-called "Chicago seven":  James Ingo Freed, Tom Beeby, Larry Booth, Stuart Cohen, James Nagle, Stanley Tigerman, and Ben Weese. Today, the city's skyline is among the world's tallest and most dense.

1399 Willis Tower

Willis Tower (known also as Sears Tower) is a 108-story, 442m skyscraper completed in 1973. It surpassed the World Trade Center towers in New York to become the tallest building in the world, a title held for nearly 25 years. Its innovative design, structurally efficient and economic, inspired by an advertisement for a package of cigarettes, was realised by the architect Bruce Graham and structural engineer Fazlur Rahman Khan, who used for the first time bundled tube structure. The tower's observation deck (the Skydeck), located on the 103rd floor, is 412m high and is one of the most famous tourist attractions in Chicago.

1400 Willis Tower and Wacker Drive

Presidential Towers is a series of four nearly identical towers with 49 storeys (141m), each a step back from the leader, and spanning two city blocks. Designed by Solomon Cordwell Buenz & Associates and built between 1985 and 1986, it was one of the pioneering residential projects in the River West neighborhood, an area that was once seen as nothing more than a ramshackle collection of old brick warehouses. 333 West Wacker Drive is an office building with a height of 149m, designed by Kohn Pederson Fox Associates and completed in 1983. On the side facing the Chicago River, the building features a curved green glass façade, while on the other side the building adheres to the usual rectangular street grid.

John Hancock Center is a 100-story, 344 m supertall skyscraper located in the Magnificent Mile district, which was changed the name to 875 North Michigan Avenue in 2018. Bruce Graham was chief designer, and structural engineer Fazlur Rahman Khan. When the building topped out on May 6, 1968, it was the second-tallest building in the world and the tallest outside New York City. The building is home to several offices and restaurants, as well as about 700 condominiums. From the 95th floor restaurant, diners can look out at Chicago and Lake Michigan. The observatory (360 Chicago) competes with the Willis Tower's Skydeck.
About the stamps
On the postcard 1397
The first stamp is part of the Wedding series, about which I wrote here. The second stamp is part of the series Send a Hello (Forever), about which I wrote here.

On the postcard 1398
The first stamp, depicting Spicebush Swallowtail, is part of a definitive series with butterflies, about which I wrote here. The second belong to the series issued on 2013 to commemorate the Harry Potter film series, about which I wrote here.

On the postcard 1399
The first stamp is part of the Wedding series, about which I wrote here. The second belong to the series issued on 2013 to commemorate the Harry Potter film series, about which I wrote here.

On the postcard 1400
The first stamp is part of the series Send a Hello (Forever), about which I wrote here. The second stamp is part of the Wedding series, about which I wrote here.

On the postcard 3432
The first stamp is one of the two issued on July 19, 2019, to celebrate the 50th anniversary of Apollo 11 and man's first steps on the Moon. Art director Antonio Alcalá designed the stamps. The 1969: First Moon Landing stamps are being issued as Forever stamps. The first stamp, depicting read pears, is part of the series of definitives stamps Fruits, about which I wrote here.

The last stamp was issued on January 17, 2019 to mark The Lunar New Year - Year of the Boar.

References
Chicago - Wikipedia
Chicago skyline guide - Wikitravel
Chicago/Loop - Wikitravel
Willis Tower - Wikipedia
Presidential Towers - Chicago Architecture Info 
333 Wacker Drive - Chicago Architecture Info
333 Wacker Drive - Wikipedia

Sender 1397-1400, 3432: Denise 
1397-1400: Sent from Greenvale (New York / United States), on 17.01.2014
1397, 1399: Photo - Karina Wang 
1398: Photo - Terry Shoulders
1400: Photo - Phil Valdez
3432: Sent from Jericho (New York / United States), on 04.02.2020
Photo - Christopher Arndt