DT made the announcement Tuesday after hyping up the fact the day prior he was going to pardon someone major, saying Anthony shouldn't have been found guilty for casting a vote in the presidential election of 1872 ... which was illegal for women to do back then.

It's a bizarre choice and comes off as a desperate appeal to women before the November election -- especially on the 100-year anniversary of the passage of the 19th Amendment. We get it ... but fact is, there's plenty of still-living people that could've used the pardon now.

Still, since we're talking SBA -- here's the story on her conviction ... which was issued under sketchy circumstances and probably didn't need official rectifying all these years later.

Susan broke the voting law in protest that year when Ulysses S. Grant was facing off against Horace Greeley. Like we said, only men were allowed to cast ballots in those times -- but the women's suffrage movement was in full swing ... and Susan was leading the charge. She and about a dozen other women were given access to the booths.

She was one of many arrested and tried for voting -- but the judge presiding over her case actually directed the jury to hand down a guilty verdict, which they did. All she had to do was pay a $100 fine, but she resisted ... standing on principle she'd done nothing wrong.