From the U.S. Postal Service announcement on November 17, 2020:From the USPS: This stamp celebrates the bicentennial of Missouri statehood. Missouri became the 24th state in the Union on Aug. 10, 1821. The stamp art is an existing photograph of Bollinger Mill State Historic Site by noted landscape photographer Charles Gurche. Art director Greg Breeding designed the stamp.

Official site

Wikipedia

This stamp will be issued August 10th with a ceremony in Jefferson City, Mo.

Additional information will be posted below the line, with the most recent at the top.

Updated October 4th:
The Scott catalogue number for this issue is 5626.

Updated July 7th:
Here are the first-day postmarks for this issue: The Digital Color Postmark for this issue measures 2.60″ x 1.46″. The pictorial postmark measures 2.28″ x 1.24″

Updated July 1st from the Postal Bulletin:
On August 10, 2021, in Jefferson City, MO, the United States Postal Service® will issue the Missouri Statehood stamp (Forever® priced at the First-Class Mail® rate) in one design, in a pressure-sensitive adhesive (PSA) pane of 20 stamps (Item 481100). This stamp will go on sale nationwide August 10, 2021, and must not be sold or canceled before the first-day-of-issue.

This stamp celebrates the bicentennial of Missouri statehood. Missouri became the 24th state in the Union on August 10, 1821. The stamp art is a photograph taken of Bollinger Mill State Historic Site. The photo shows the multi-story mill, which dates to the Civil War period, as well as the Burfordville Covered Bridge, Missouri’s oldest covered bridge and one of only four that remain in the state. Noted landscape photographer Charles Gurche, who took this shot, began his photography career in Missouri. Art director Greg Breeding designed the stamp with an existing photograph by Gurche.

Automatic distribution only in Missouri.

How to Order the First-Day-of-Issue Postmark:
Customers have 120 days to obtain the first-day-of-issue postmark by mail. They may purchase new stamps at their local Post Office™ or at The Postal Store® website at usps.com/shop. They must affix the stamps to envelopes of their choice, address the envelopes (to themselves or others), and place them in a larger envelope addressed to:

FDOI – Missouri Statehood Stamp
USPS Stamp Fulfillment Services
8300 NE Underground Drive, Suite 300
Kansas City, MO 64144-9900

After applying the first-day-of-issue postmark, the Postal Service™ will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. There is a 5-cent charge for each additional postmark over 50. All orders must be postmarked by December 10, 2021.

Technical Specifications:

Issue: Missouri Statehood Stamp
Item Number: 481100
Denomination & Type of Issue: First-Class Mail Forever
Format: Pane of 20 (1 design)
Series: Statehood
Issue Date & City: August 10, 2021, Jefferson City, MO 65101
Art Director: Greg Breeding, Charlottesville, VA
Designer: Greg Breeding, Charlottesville, VA
Existing Photo: Charles Gurche
Modeler: Sandra Lane / Michelle Finn
Manufacturing Process: Offset, Microprint
Printer: Banknote Corporation of America
Press Type: Gallus RCS
Stamps per Pane: 20
Print Quantity: 18,000,000 stamps
Paper Type: Phosphor, Block Tag
Adhesive Type: Pressure-sensitive
Colors: Black, Cyan, Magenta, Yellow
Stamp Orientation: Horizontal
Image Area (w x h): 1.42 x 0.84 in. / 36.068 x 21.336 mm
Overall Size (w x h): 1.56 x 0.98 in. / 39.624 x 24.892 mm
Full Pane Size (w x h): 7.24 x 5.92 in. / 183.896 x 150.368 mm
Press Sheets Size (w x h): 11.84 x 21.72 in. / 300.736 X 551.688 mm
Plate Size: 120 stamps per revolution
Plate Number: “B” followed by four (4) single digits in all corners
Marginal Markings:
Front: Plate number in all corners
Back: ©2020 USPS • USPS logo • 2 barcodes (481100) • Plate position diagram (6) • Promotional text

Updated June 26th:

[press release]
Missouri Stamp to Honor State Bicentennial

WHAT: On Aug. 10, 1821, Missouri was admitted as the 24th state in the Union. In 2021, the U.S. Postal Service celebrates the state’s bicentennial with a new stamp.

The first-day-of-issue event for the Missouri Statehood Forever stamp is free and open to the public. News of the stamp is being shared with the hashtags #MissouriStatehood, #MissouriStatehoodStamp and #Statehoodstamps.

WHO: Peter Pastre, vice president, Government Relations and Public Policy, U.S. Postal Service, will serve as dedicating official.

WHEN: Tuesday, Aug. 10, 2021, at 9 a.m. CDT

WHERE: Missouri State Capitol
201 W Capitol Ave.
Jefferson City, MO 65101

RSVP: Dedication ceremony attendees are encouraged to RSVP at: usps.com/missouristatehood

BACKGROUND: The westernmost state when it entered the Union in 1821, Missouri was a natural resting place for settlers before continuing their journey to claim lands acquired in the Louisiana Purchase of 1803.

With 91 state parks and historical sites and hundreds of conservation areas, Missouri has an abundance of places to enjoy hiking, camping, fishing and other activities. It boasts world-renowned public gardens, world-class museums, several National Historic Trails, and professional sports teams including baseball, football, soccer and ice hockey.

Missouri is home to great food and great music. Some of the country’s best blues music is performed in concerts and clubs across the state. Whether it is Kansas City or St. Louis-style, Missouri is famous for its barbecue.

The people of Missouri are said to be stalwart and noncredulous, unswayed by eloquent speeches and unconvinced without adequate evidence, hence the state nickname: The Show-Me State.