It is probable that Edward Ketcham is the progenitor of all Ketchams in America (with the exception of rumors of a native American Ketcham line).  While likely, it is only probable because two caveats have been noted: the mysterious Henry Ketcham and the "Scottish Ketchams."

A Henry Ketcham is found in  Ipswich, Massachusetts, in 1638. (Savage 1990, vol. 3, p. 14.) According to the published genealogies, we know nothing further of Henry Ketcham or his descendants.  While the presence of Henry Ketcham is troubling for a definitive answer to the question, Henry Ketcham is almost certainly related to Edward Ketcham.  If Henry is not Edward's son, they are likely brothers. It is highly unlikely that two unrelated Ketchams would be found in Ipswich together in 1635.  If that is the case, the progenitor of all Ketchams (assuming Henry's descendants are in fact among us), is Edward's and Henry's father -- an as yet unnamed "Ketcham" who is the progenitor of us all.

Some of the Ketcham genealogies also allege the existence of Scottish "Ketchams," a Scottish clan whose name (in Gaelic) is spelled differently than "Ketcham" but which sounds similar.  None of the books used in research give any further information, or the source of this story.

Edward Ketcham was reportedly born at County Kent, England and married Mary Hall August 22, 1619 at Church of St Andrew the Great, Cambridge, England. Also married Sarah Salmon at Southold, Suffolk Co, New York; died before June 6, 1655 at Stratford, Fairfield County, Colony of Connecticut; died June 19, 1655 at Stratford, Fairfield County, Colony of Connecticut.

There is an unsubstantiated story that he resided before 1619 at Ipswich,

He immigrated in 1629 to Massachusetts Bay Colony; on the ship Hopewell.
He immigrated on July 3, 1630 to Massachusetts Bay Colony; on board the ship Hopewell. 
He immigrated in 1631 or 1632 to Massachusetts Bay Colony; on the ship Lyon.
He immigrated in 1635 to Massachusetts Bay Colony; on board the ship Nector.

According to Captain William Moore. He resided between 1635 and 1640 at Ipswich, Massachusetts Bay Colony. 

Edward Ketcham was according to some, present when a group from Antiqua, West Indies, made an agreement to establish a settlement on Hashamomuck Neck on the eastern tip of Long Island in the south hold of the New Haven Colony (now Southold, Suffolk Co, New York) in 1636 at Long Island, New York. 

He took the oath to become a Freeman on March 9, 1636 or 1637 at Ipswich, Massachusetts Bay Colony (Massachusetts). The Oath of a Freemen agreed upon at the Genall Court, May 14th, 1634. 

"I, A B, etc., being by Gods pvidence an inhabitant & freeman within the jurisdiccon of this comon weale, doe freely acknowledge my selfe to be subiect to the goument thereof, & therefore doe here sweare by the greate and dreadfull name of the euer lyveing God that I wilbe true & faithful to the same, & will accordinly yeild assitance & support therevnto, with my pson & estate, as in equitie I am bound, & will also truely indeavr to mayntaine & preserue all the liberties & previlidges thereof, submitting my selfe to the wholesom lawes made & established by the same ; and further, that I will not plott or practise any euill against it, nor consent to any that shall soe doe, but will tymely discouer & reveale the same to lawfull aucthority nowe here established for the speedy preventing thereof. Moreouer, I doe solemnly bind my selfe in the sight of God, that when I shalbe called to giue my voyce touching any such matter of this state, wherein ffreemen are to deale, I will giue my vote & suffrage as I shall in my owne conscience iudge best to conduce & tend to the publique weale of the body, without respect of psons or favr of any man. Soe helpe me God in the Lord Jesus Christ."15,16 He and 56 other men of Ipswich signed a remonstrance against the departure of John Winthrop Jr on 21 Jun 1637 from Ipswich, Massachusetts Bay Colony (Massachusetts).17 He was shown as a landowner and cattleowner on 20 Dec 1638 at Ipswich, Massachusetts Bay Colony (Massachusetts).18,19 He was shown as a cattle owner on 30 Jun 1639 at Ipswich, Massachusetts Bay Colony (Massachusetts). He was listed as cattle owner on 13 Jan 1640 at Ipswich, Massachusetts Bay Colony (Massachusetts).20,21,22 He was a witness when John Woolridge and Hester Ketcham were "Hester Ketcham is freed from her service wth her mr, John Woolrige, & the said mr enjoyned to give ^ Ketcham 20shs charges, & the said mr, John Woolrige, is bound to his good behavior, & enjoyned to appear at the Court the 7th m next, & to put in sufficient caution for the good behavior & appearance./" on 3 Mar 1639/40 at Boston, Massachusetts Bay Colony.23,24 He resided before 1650 at Hashamomuck Neck, the southold (Southold), (Suffolk Co), New Haven Colony (New York), when he was listed as land owner.25 He left a will on 9 Jun 1655 at Stratford, (Fairfield Co), Colony of Connecticut (Connecticut); inventory taken, amounted to 90/11/6.26
 
 

credit: John M. Ketcham