234 years ago, the Declaration of Independence was adopted:
The Washington Post just announced, spectroscopic and chemical analyses of Jefferson's four-page "original Rough draught" have shown that the word originally written instead of "citizens" was "subjects".
The word "subject" is known to have appeared in a draft of the Virginian constitution, too.
If I understand well, the word appeared in the last two paragraphs of the long rant against the British king:
...The contemporary sources usually argue that by replacing the word, Jefferson saved the spirit of America, and all this stuff. Well, I don't buy it.
He has constrained our fellow subjects [Citizens] taken Captive on the high Seas to bear Arms against their Country, to become the executioners of their friends and Brethren, or to fall themselves by their Hands.
He has excited domestic insurrections amongst us, and has endeavoured to bring on the inhabitants of our frontiers, the merciless Indian Savages, whose known rule of warfare, is an undistinguished destruction of all ages, sexes and conditions.
I actually think that he had - and they had - good reasons to use "subjects" instead of "citizens" because it is a more technical term that emphasizes that the people living in the new kind of a country will have a different status than the "citizens" of existing empires such as Great Britain - which pretty much universally originated from feudal systems.
The word "subjects" used for all kinds of Americans including the slaves isn't terribly flattering or warm but it has its advantages for themselves, too. It linguistically gives them a proper degree of independence of any government structures. It would induce less vibrant emotions but it would more accurately express the founding fathers' intent to create a new country "from the bottom".