William Milliken, Sr. was born about 1715, the son of Samuel Milliken. His place of birth was perhaps in Ireland. Some researchers have disputed the information that he was born on a specific date in Dromore, County Down.

He married Jane White in about 1740 in Pennsylvania. She was born in 1722 and died in 1758. Jane White was most likely the granddaughter of Alexander White, whose will was proved in May 1743 (Chester County, Jane White was most likely the granddaughter of Alexander White, whose will was proved in May 1743 (Chester County, Pennsylvania records). The Will names a wife, Jane, and several children, including sons Alexander, John, and David, but no daughter, Jane.

Among William and Jane's known children were:  

• Abigail was born in about 1741 and married John Frazier.
• Samuel was born on 11 December 1742 and married Ann Baldwin.
• Sarah was born in 1743 and married John Mills.
• David was born in 1745
• Mary was born on 24 June 1747 and married Robert Bratton.
• Martha was born in about 1748
• William was born on 7 January 1753 and married Eleanor Smith.
• Benjamin was born on 21 January 1755 and married Rebecca Rush.
• Hannah was born in 1756 and married Enos Blair.
• Alexander was born in 1757

He may have had a second wife, also named Jane.

He appears on the tax list of Chester County, Pennsylvania, from 1739 to 1758, and is crossed off in 1758. A colonial tax list suggests that he was already in North Carolina in 1755. Still, there is also evidence that places him in Pennsylvania that year, so it is possible that he came south to purchase land and returned to Pennsylvania before moving his entire family.

He is listed as unmarried in the 1739 and 1740 Chester County tax lists. The 1741 tax list is missing, but since the oldest daughter, Abigail, must have been born by about 1741, he probably married his first wife, Jane White, in 1740. We think she is probably the mother of all his children.  There is a monument at Springfield Friends Cemetery in Guilford County, North Carolina, giving Jane's death date as 1758. However, this is not a contemporary marker, and she presumably is not actually buried there since the Springfield Meeting wasn't organized until about 1773. Thus, there is some uncertainty as to whether Jane died in Pennsylvania before William's having moved his family south or if she died soon after they arrived in North Carolina. The Quaker marriage record for Sarah Millikan in 1761 lists her as the daughter of only William, not of William and Jane, as would be expected if her mother were living. This supports the notion that the wife Jane, who appears with William in later records, is a different woman.

William does appear in records in North Carolina with a wife named Jane, however. Brenda Haworth's manuscript prepared for the Springfield Memorial Association puts the marriage to this Jane as 1775 but doesn't cite a marriage record. However, there is a deed on 14 October 1766, Rowan County Deed book 6:309, "William Milliken and wife Jane to Samuel Milliken for 10 sh proc, 200 A on Muddy Crk on W side Deep R." Nathan Farlow, John Buefero witnesses. Proved October court 1766 [abstract by Jo White Linn]. Is this possibly a leftover deed from a 1758 transaction, referring to Jane White [which would then be evidence that she came to North Carolina], or does this refer to the second Jane, in which case that marriage must have occurred between 1761 and 1766?

A Quaker, William did not bear arms during the Revolution, but he is listed in the DAR Patriot Index:  "He was so obnoxious to the Tories that on March 10, 1782, Colonel Fanning burned his home and barns with all their contents. [William] also furnished supplies."

Loose estate papers at the North Carolina Archives include an estate inventory for William, December court 1793, by Samuel Milliken, administrator. A Jane Milliken appears in a list of people who purchased or received items from his estate. She got lots of furniture, a saddle and bridle, a colt, a pot oven, and a skillet, substantially more individual items than most other purchasers. Is this his widow or a granddaughter?

A 1974 letter in the Millken file at Guilford College from Mrs. Kenneth Brant of Wichita, Kansas, names William's second wife as Jane Brown.  No documentation was given.

The Patriot died in 1793 in Randolph County, North Carolina.