Updated: Feb 2026
The St. Mary’s County (SMC), Maryland branch of the family began with the arrival of John Cissell (Cecill) in 1658. He died there in 1698. His birth date is generally taken as about 1638. His birthplace and parents are not known and there are no records to provide this information. He was a farmer and, although not literate, did acquire a fair amount of property during his lifetime in Maryland.
We have developed a theory about how he may have come to SMC in 1658. Around 1650, England was actively working to challenge Spanish dominance in the Caribbean. The most significant effort came in 1655 with Cromwell’s “Western Design” — an expedition led by Admiral William Penn and General Robert Venables with about 2,500 soldiers. After failing to capture Santo Domingo in Hispaniola, they successfully took Jamaica in May 1655. Troop morale was very low and many soldiers deserted. It is possible that John may have been impressed into this English force and, rather than returning to England, made his way to SMC after the capture of Jamaica.
From John’s will and the few surviving land records, we know that he had seven sons: John, William, Thomas, Richard, Robert, Edward, and James. Except for his will, there seem to be no other records related to Richard, Robert, or Edward, and it is assumed that they died young and had no children.
There were a few Cissells in SMC in the 1700s for whom records do not provide family connections. One of these is John Baptist Cissell (ca. 1741 SMC – ca. 1799 KY). Our DNA results, using the BigY test at FTDNA, show that he was a descendant of John Cissell, possibly through his eldest son, John.
Over the years, several suggestions have been proposed as to who John Cissell’s wife was. This question is complicated by an unusual entry in the 1701 land records.
In his will, John Cissell bequeathed the properties he owned, amounting to about 500 acres in total, to members of his family. His will did not specifically identify his dwelling plantation, but it is generally taken to have been “Poplar Neck.” The will gave this property to his wife “Mary.” After her death it was to go to his son Edward Cissell; but if Edward did not reach the age of 21 or have children, the land was to go to his son James.
In the land records for 1701, about three years after John’s death, the 200 acres of Poplar Neck were allocated as follows: William Cissell (25 acres); James Cissell (25 acres); Thomas Cissell (50 acres); Mary Dant (50 acres); and Thomas Cissell (50 acres). Who was the Mary Dant in possession of 50 acres of the original home plantation? And why was Mary Cissell not listed?
However, several St. Mary’s County researchers, including Linda Reno, investigated this theory and concluded that Mary Shirtcliffe could not have married John Cissell. The complete analysis will not be repeated here, but the general argument relates to the fact that Mary Shirtcliffe had originally married Peter Mills and then, after his death, had married John Dant. Peter had been married previously before coming to Maryland. With Peter, she had at least three children. Given the dates and times involved, and the fact that John Cissell had at least seven children of his own, she could not possibly have also married John Cissell.
If John Cissell’s wife was not Mary Shirtcliffe, who was the Mary Dant on the land records and why was Mary Cissell not listed there? A possible solution to this long-standing mystery was proposed in an article, “The Maryland Cissell Family,” for the Winter 2018 issue of the Chronicles of St. Mary’s, the journal of the St. Mary’s County Historical Society. The argument was that John’s wife was actually Mary Mills, a daughter of Peter Mills from his first wife.
A main reason for considering Mary Mills was a 1672 denization record in the Maryland historical records. A letter of denization is a 1600s version of a green card:
July 12th 1672 Letters of denization issued under the Great Seal of this Province unto Mary Mills Daughter of Peter Mills of Saint Marys County
There are several possibilities as to why Mary Cissell may not have been listed on the land records for Poplar Neck. Mary Mills had apparently been born in Holland. As a non-English citizen, she would not have been able to legally inherit property in Maryland and so would not be listed on the land records. Another possibility is that Mary Cissell could well have died about the same time as John Cissell. In either case, some of her property could have gone to her mother-in-law, then Mary Dant (an actual English citizen and able to own land). And so the Mary Dant in the land records was still most likely Mary Shirtcliffe, but she had not been the wife of John Cissell.
Can DNA testing be used to verify that Mary Mills was actually John Cissell’s wife? The answer is yes, but not very easily. Normally, one could test several members of the Mills and Cissell families using Ancestry.com or Family Tree DNA’s Family Finder tests. These can easily verify family connections back four or maybe five generations. Unfortunately, the time back to John Cissell and his wife is now about 11–13 generations. Since ½ of the DNA from each line is lost each generation, there will be little or no useful DNA left after 11-13 generations for these tests to detect. So to use these specific tests, one would probably have to exhume some of the great-great-grandchildren of John Cissell and Peter Mills to get useful information!
As another approach, it seemed appropriate to try whole genome sequencing (WGS). We hoped that at least some small portions of Peter’s 3 billion base-pairs of DNA might have been transferred down to his living Mills descendants and also, through his daughter Mary, to one or more of John Cissell’s living descendants.
John and Peter do have living descendants. If Mary Mills had been John’s wife, these descendants would share the common ancestor Peter Mills about 13 generations back. We wanted to see if WGS data could detect any shared DNA segments and so support the Mary Mills hypothesis.
Technical Note: DNA segments that are “identical by descent” (IBD) are inherited from a common ancestor. When segments contain rare genetic variants (SNPs — single nucleotide polymorphisms), they are more likely to represent true ancestral connections rather than chance matches. Segment length is measured in centimorgans (cM), with longer segments indicating more recent common ancestry.
We obtained WGS data for three of John’s descendants (Dave, Jason, and Clemie) and one descendant of Peter. We focused on identifying rare shared SNPs, which are more likely to indicate true IBD (identical by descent) segments than common variants.
Starting with the variant call format (VCF) files for all four individuals, we developed a bioinformatics pipeline using bcftools and Python scripts (with assistance from AI tools for coding). We filtered for rare SNPs with allele frequencies <0.001 based on the Genome Aggregation Database (gnomAD v2.1.1, non-Finnish European population). We then identified regions where pairs of individuals shared these rare SNPs.
We found between 89–171 shared rare SNPs across the various appropriate pairwise individuals, suggesting connections between them. The most interesting result was between one of John’s descendants, Jason, and Peter’s descendant. On Chromosome 5, they share an approximately 0.80 cM segment containing 95 rare SNPs.
While 0.80 cM is far below the threshold for Family Finder matches (typically 6–7 cM minimum), the density of 95 rare SNPs in such a short segment is highly unlikely to occur by chance. This suggests a genuine IBD segment inherited from a common ancestor.
The WGS analysis provides genetic support for the hypothesis that Mary Mills was John Cissell’s wife. The shared rare SNP segment between descendants of John Cissell and Peter Mills is consistent with them sharing a common ancestor through Mary Mills approximately 12-13 generations ago. While this finding does not constitute absolute proof, it represents the strongest genetic evidence available given the considerable time depth involved.