(Cancel would be from 1891, rather than 1881. Stamp not issued in the 1880s)
Name standardization was one of PMG John Wanamaker's legacies. Particularly in the 1893-1895 era there are hundreds of post offices which had small changes in their names. It was a gradual process over several years. These are particularly noticeable when looking for opening/closing dates in post office lists like found on Jim Forte's webpage.
Some of the more notable standardizations:
-borough to -boro
-burgh to -burg.
-centre to -center
place condensations like Le Roy to Leroy and La Fayette to Lafayette.
possessive names lost their apostrophe, etc.
Pittsburgh, PA resisted.
In the case of Galesburgh, Postal Bulletin #4018 dated May 8, 1893 has:
Out of necessity, offices might continue to use their old devices until the new ones arrived.
Add: As I keep digging ... Marshall Cushing's wonderful and extremely useful1893 volume "The Story of Our Post Office" has a more contemporary account on page 282: