The USPS will offer two postmarks to commemorate the 2025 inauguration:
The dimensions are 2.72″ x 1.26″ 
This postmark measures 3.38″ x 1.0″
The Inauguration Day postmarks will be available only from Cancellation Services in Kansas City:
Inauguration Day Postmarks
Cancellation Services
8300 NE Underground Drive, Pillar 210
Kansas City MO 64144-0001
Send your envelopes and cards to this address, with sufficient postage on each to meet the first-class rate (such as a Forever stamp, or a combination equaling or exceeding 73¢)
Updated January 21:
I was surprised at the paucity of postmarks, given that PMG Louis DeJoy [right] was a major donor to President Trump’s first presidential campaign and was picked by the Postal Service’s Board of Governors, all of whom were appointed by Trump. But the Washington Post reports that not only are they no longer friendly, but the Trump team is looking to oust DeJoy. A key reason, WaPo says, was the postal agency’s support of voting-by-mail in the 2020 election. [You made need a subscription to read the full story.] —LdeV
How can I receive the cancel?
Send your cards and covers to the address shown.There is no charge for quantities of less than 50 but the “covers” must have sufficient postage to meet the first-class rate (73¢, or a Forever stamp).
Can I send a prepaid return envelope with my covers so they are not spoiled with over-cancellations in regular mail priocessing?
Yes. In fact, that’s the way I think most people will do it. Just make sure both the outer envelope and each envelope for servicing have enough postage on them.
Do you know how long they will offer it / when it must be postmarked by? Thanks!
I’d guess 30 days, so postmarked no later than February 20th. (which is actually 31 days but that’s usually the way it works)
Thank you!
Where did you see thi announcement? I’m not seeing it on the USPS website or postal bullitens anywhere
It was emailed to me by the USPS, probably as part of its Cancellation Services customer base.
These two postmarks were eMailed to ‘Media Reps’, and MIGHT be in the 23 JAN 2025 Postal Bulletin.
Why are the Inauguration Day postmarks not available by covers sent to Washington DC as previously done in other years? I have already sent some covers for processing to the Massachusetts Avenue address.
There is also a Color Cached Envelope with a Color Postmark.
USPS# 882160 @ $12.95 USPS Collectors Zone
https://store.usps.com/store/product/2025-presidential-inaugural-cachet-S_882160
Can you ask for these 2 postmarks on the same cover? Of course I will put 2 first class