William "Willis" Theodore Dennison was born between 1852-1855 in Westport, Clinton County, Pennsylvania to Hiram Dennison & Louisa (née Whaling). William's birth mother, Louisa died sometime between 1855-1859 and his father, Hiram remarried to Elizabeth (née Weaver) on February 17, 1859.

1860 Census: Chapman, Clinton, PA
Name: William Dennison
Age: 8
Birth Year: abt 1852
Gender: Male
Birth Place: Pennsylvania
Home in 1860: Chapman, Clinton, Pennsylvania
Post Office: Youngwomanstown
Dwelling Number: 109
Family Number: 109

Household Members
Hiram Dennison 51 (Father)
Elizabeth Dennison 47 (Step Mother)
Jane Dennison 15 (Sister)
Andrew Dennison 9 (Brother)
*William Dennison 8
Mary Dennison 5 (Ella or another sister?)
John Dennison 3 (Brother)

1870: Keating, Clinton, PA
Name: William Denison [Dennison]
Age in 1870: 18
Birth Date: abt 1852
Birthplace: Pennsylvania
Dwelling Number: 74
Home in 1870: Keating, Clinton, Pennsylvania
Race: White
Gender: Male
Post Office: Westport
Occupation: Laborer
Attended School: Yes
Inferred Father: Hiram Denison
Inferred Mother: Elizabeth Denison

Household Members
Hiram Denison 65 (Father)
Elizabeth Denison 57 (Step Mother)
Andrew Denison 21 (Brother)
*William Denison 18
Ellen [Ella] Denison 15 (Sister)
John Denison 13 (Brother)

William T. Dennison married Amanda Jane (nee Smith), daughter of Hugh Smith and Caroline (nee Lininger) Smith on July 4, 1872 in Renovo, Clinton County, Pennsylvania.

MARRIED.
DENNISON-SMITH-On July 4, at Renovo, by John Reilley, Esq., William T. Dennison to Miss Amanda Jane Smith, both of Clinton county, Pa.
Publication Source:
Clinton Democrat, 07/18/1872
Renovo Record, 07/11/1872

Little is known regarding what transpired following his marriage to Amanda, but some time between the 1872-1885, William relocated from Clinton County, PENNSYLVANIA to Clinton County, IOWA.

William remarried to Rhoda E. Seymour, daughter of Oscar W. Seymour and Elizabeth (nee Nixon) on November 14, 1885. According to Clinton County, Iowa birth records, William and Rhoda had an unnamed daughter born on March 26, 1887. Rhoda died on April 6, 1887 and was buried in Springdale Cemetery in Clinton County, Iowa.

Following Rhoda's passing, William remarried to Kittie S. (nee Austin), daughter of Joseph James Austin & Malinda "Maud" (née Snyder) Austin on May 22, 1888 in Clinton County, Iowa.

William died on November 23, 1895 in Grandin, Carter County, Missouri and was buried in Springdale Cemetery in Clinton County, Iowa.

DENNISON
The remains of W. Dennison, brother-in-law of J.L. Austin, of this city and who died at Grander, Mo., arrived here Sunday night. The funeral services were held at the residence of Dr C.W. Myers at 2 o'clock Monday afternoon, with interment in Springdale. Rev. Hulbert officiated.
Publication: Clinton Morning Age Date: November 26, 1895 City: Clinton, Iowa, United States of America page 4

Following William's death, Kittie moved to Cedar Rapids from Clinton Iowa in 1897. She remarried to Bertram "Bert" D. Millholen, son of James Millholen and Mary T. (née Davis) Millholen on June 14, 1899 in Cedar Rapids, Iowa.