Entry in progress—B.P.
 
Wikiquote: Benjamin Franklin
Benjamin Franklin (17 January 1706 – 17 April 1790) was an American inventor, journalist, printer, diplomat, and statesman.
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Attributed
. We must, indeed, all hang together, or assuredly we shall all hang separately.
..Statement at the signing of the Declaration of Independence (1776-07-04), quoted as an anecdote in The Works of Benjamin Franklin by Jared Sparks (1840). However, this had earlier been attributed to Richard Penn in Memoirs of a Life, Chiefly Passed in Pennsylvania, Within the Last Sixty Years (1811, p. 116).
     
Wikipedia: Richard Penn (governor)
Richard Penn (c. 1734 – 27 May 1811) served as the Lieutenant Governor of the Province of Pennsylvania from 1771 to 1773, and was later a member of the British Parliament.
 
Penn, of Laleham in Middlesex, was the second son of Richard Penn, Sr. (died 1771) and the grandson of the William Penn, founder of Pennsylvania. He was educated at Eton College and St John’s College, Cambridge before joining the Inner Temple. In 1763 he and his brother John visited to Pennsylvania, of which his family were still sole proprietors. He was qualified as a councilor on January 12, 1764. In 1771 he was appointed Lieutenant Governor, and became Acting Governor when his brother returned to England to attend to the colony’s legal interests. He proved popular with the provincials, taking much care over their commercial interests, but less so with his uncle, the Proprietor. After two years he was supplanted by the re-appointment of his brother as governor.
 
Penn entertained the members of the Continental Congress at his Philadelphia city house, George Washington being among his guests. He returned to England in the summer of 1775, when the Continental Congress entrusted him with the Olive Branch Petition to the King. George III refused to accept the petition, but Penn gave evidence to the House of Lords on the colonies’ attitudes toward independence. After the conclusion of the American Revolution, he was allowed compensation by the US government for the loss of his proprietary rights in Pennsylvania, and visited Philadelphia again in 1808. James Boswell (who was a friend of Penn’s) records that in 1789 the influential Earl of Lonsdale urged the government to appoint Penn as Britain’s first Ambassador to the United States, although nothing came of the idea.
   
The Yale Book of Quotations
Edited by Fred R. Shapiro
New Haven, CT: Yale University Press
2006
Pg. 288:
Benjamin Franklin
U.S. statesman, scientist, and author, 1706-1790
“We must all hang together, or most assuredly we shall all hang separately.”
Remark at signing of Declaration if Independence, Philadelphia, Pa., 4 July 1776. P.M. Zall, Ben Franklin Laughing (1980) , records that this attributed remark appears in American Joe Miller (1839) and Works of Benjamin Franklin (1840). Zall also points out, however, that it had earlier been ascribed to Richard Penn (American Anecdotes [1830]) and that Carl Can Doren regards it as not an authentic Franklinism (Benjamin Frankling [1938]).
 
Google Books
Life,
A comedy, in five acts,
as performed at the Theatre-Royal, Convent-Garden.
By Frederick Reynolds
The Fourth Edition
London: T. N. Longman and O. Rees
1801
Pg. 34: 
Craft. So I do. (Exit JONATHAN.)
Pg. 35:
And as I mean to touch a third of his fortune, I must keep him in the dark about the young couple—yes; much as I detest, I must not expose them—for, as the joke goes, if we don’t hang together, by Heavens we shall hang separately.
     
22 December 1808, Hampshire Federalist (MA), pg. 3:
A certain democratic sage of the house of representatives, in debate declared, that if they (his party) did not hang together, they might be hung separately!
 
Google Books
Memoirs of a life, chiefly passed in Pennsylvania, within the last sixty years : with occasional remarks upon the general occurrences, character and spirit of that eventful period.
By Alexander Graydon
Harrisburgh, PA: Printed by John Wyeth
1811
Pg. 115:
Both the brothers, John and Richard Penn, had been governors of Pennsylvania; the former being in office at the beginning of hostilities. By yielding to the torrent, which it would have been impossible to withstand, he gave no offence, and avoided reproach; though it was deemed expedient to have him secured and removed from Philadelphia, on the approach of the royal army in the year 1777. Mr. Richard penn, having no official motives for reserve, was even upon terms of familiarity with some of the most thorough going whigs, such as general Lee and (Pg. 116—ed.) others: An evidence of this was the pleasantry ascribed to him, on occasion of a member of congress, one day observing to his compatriots, that at all events “they must hang together:” “If you do not, gentlemen,” said Mr. Penn, “I can tell you that you will be very apt to hang separately.”
 
Google Books
The Modern Theatre:
A collection of successful modern plays as acted at The Theatres Royal, London
Vol. I
Selected byy Mrs. Inchbald
London:Hurst, Rees, Orme, and Brown
1811
Pg. 143:
LIFE;
A
COMEDY,
AS IT IS PERFORMED AT THE
THEATRE-ROYAL, CONVENT-GARDEN.
BY
FREDERICK REYNOLDS.
Pg. 176:
Craft. So I do. (Exit JONATHAN.) And as I mean to touch a third of his fortune, I must keep him in the dark about the young couple—yes; much as I detest, I must not expose them—for, as the joke goes, if we don’t hang together, by Heavens we shall hang separately.
   
14 April 1819, American Beacon, (VA), pg. 2: 
Old Mr. Penn, when he took leave of the Philadelphians, during the war for Independence, said to them, unless you hang together, you’ll all hang separately;...
 
18 November 1824, Boston (MA) Commercial Gazette, pg. 4:
REVOLUTIONARY ANECDOTE.
Richard Penn, one of the proprietors, and of all the governors of Pennsylvania, under the old regime, probably the most deservedly popular, in the commencement of the revolution, (his brother John being at that time governor) was on the most familiar and intimate terms with a number of the most decided and influential whigs, and, on a certain occasion, being in company with several of them, a member of Congress observed, that such was the crisis, “they must all hang together.” “If you do not, gentlemen,” said Mr. Penn, “I can tell you that you will be very apt to hang separately.”