Only son of Hugh White, United States Congressman from New York.
Graduated from Hamilton College in Clinton New York in 1853.
Managed a family farm in Canaseraga, New York for about 10 years. This is probably Sweet Briar Farm in the town of Ossian, Livingston County, New York, which was originally owned by his father Hugh White. Ossian was in Allegheny County, New York but became part of Livingston County in 1856. William Mansfield White is in the 1870 and 1880 census for Ossian, Livingston County, New York.

He married Anna Maria Pierrepont on Jan. 23, 1863 of Pierrepont Manor, New York, daughter of William Constable Pierrepont and Cornelia Butler.
Around 1883, they moved to Utica, New York where Anna Maria died September 22, 1884 at age 42, a year after the birth of her youngest child and William Mansfield died on January 2, 1896.
There were six sons and five daughters.

A biography of William Mansfield White was written in:
Oneida County, New York Biographies by Daniel Wagner.
Our County and Its People, Part II: Biography. Pg. 89-91.
Boston: The Boston History Company, 1896.

William Mansfield White and his sister Isabel White Niles (1837-1910) wife of William Watson Niles of the Bronx, New York, (only two surviving adult children of Hugh White & Maria Mansfield) were partners in land leases in Waterford, New York (Cohoes is often mentioned and this is next to Waterford), according to papers held at the New York State Library: SC11036 Manuscripts and Special Collections-White Papers. Other papers are at Cornell.

Children:
[1.] Hugh White b. 29 August 1865 m. Theodora Miller
[2.] William Pierrepont White b, 5 April 1867 m. Mary Antoinette Wheeler.
[3.] Anna Maria White b. 14 Aug. 1868 d. 21 April 1911
[4.] Hubert Lawrence White b. 12 Oct. 1869 m. Emma Ruth Decker.
d. 15 Nov. 1953 in Los Angles CA. [gravesite unknown]
[5.] Florilla Mansfield White b. 7 Sept. 1871
[6.] Mary Pierrepont White b. 14 July 1873
[7.] Cornelia Butler White b. 2 July 1874
[8.] Isabel White b. 18 April 1876 d. 1910
[9.] DeLancey Pierrepont White b. 12 June 1878 m. Maud Mather.
[10.] Charles Carroll White b. 3 June 1880 d. 9 Dec. 1958 m. Edith Le Moyne. [gravesite unknown]
[11.] John Dolbeare White b. 26 August 1883 m. Dorothy Handy.

Granite square memorials placed in rows around the large Hugh White monument at Albany Rural Cemetery are:
1. Diana Godfrey Edmunds and her great grandfather William Mansfield White 1833-1896-In front of Hugh White and his wife Maria Mills Mansfield. Anna Maria Pierrepont, wife of William Mansfield White is in the Church/family plot at Pierrepont Manor.
2. Hugh White 1798-1870 and his wife Maria Mills Mansfield 1808-1888.
3. Three stones behind their parents: Florilla Mansfield White 1830-1852; Charlotte White Niles 1843-1864; Sarah White 1840-1844.

1870 Census:
Ossian, Livingston County, New York; Post Office Danville
[William Mansfield White & Anna Maria Pierrepont m. 1863]
186/177
William M. White Age 37 Farmer/ 63,000/ 30,00/ New York
Anna M. Age 29
Hugh Age 5
William P. Age 3
Anna M. Age 1
Hubert 8/12 born in Oct.
Aurilia Segnir? Age 45 Nurse/ b. in New York/ 5,000 Personal estate
Margaret Wilson Age 23/ Cook/ Canada/ Parents foreign
Honoria Crucin? Age 22/ Nurse/ b. in New York/ Parents foreign
Margaret Sheetly Age 18/ Waiter/b. in New York/ Parents foreign
Eliza Wilson Age 18/ Domestic servant/ Canada/ Parents foreign
George Devins Age 28/ Works on farm/ 100/ New York/ Foreign
Eliza Lund/ Age 30/ Seamstress/ New York/ Parents foreign

1875 New York State Census: Ossian, Livingston County, New York
246/ Frame/ 6,000/ Family 246/ Wm. M. White/ Age 43/ b. Saratoga Co./ Married/ Farmer/ Native/ Owner of land.
Anna M. White/ Age34/ Wife/ Jefferson Co./ Married.
Hugh White/ Age 10/ Son/ Livingston Co.
Wm. P. White/ Age 8/ Son/ Livingston Co.
Anna M. White/ Age 7/ Daughter/ Livingston Co.
Hubert L. White/ Age 5/ Son/ Livingston Co.
Florilla M. White/ Age 3/ Daughter/ Livingston Co.
Mary White/ Age 2/ Daughter/ Livingston Co.
Cordelia Burton/ Age 1/ Livingston Co.
Aurella Sigur/ Age 50/ Jefferson Co./ Single/ Housekeeper
[probably Aurella Segur 1819-13 Dec. 1895 #82202302]
M. J. Macloud/ Age 23/ Maryland/ Single/ Governess
Elizabeth Grasby/ Age 40/ England/ Single/ Cook
Margaret Hare/ Age 33/ State of Jersey/ Single/ Laundress
Eveline Keen/ Age 17/ Allegheny/ Single/ Maide
Martha Ames/ Age 17/ Steubin/ Single/ Maide
Rose Alvord/ Age 18/ Livingston/ Single/ Maide
Peter Forter/ Age 28/ Ireland/ Single/ Useful man

1880 Census: Ossian, Livingston County, New York
208/213
Wm. M. White Age 46 Farmer/ NY NY Conn
Anna M. [Anna Maria Pierrepont] Age 39/ Wife/ NY NY NY
Hugh Age 14/ Son
William P.[Pierrepont] Age 13/ Son
Anna M. Age 12/ Daughter
Hubert L.[Lawrence] Age 11/ Son
Florilla M.[Mansfield] Age 9/ Daughter
Mary Age 7/ Daughter Age 7/ Daughter
Mary Cornelia B.[Butler] Age 6/ Daughter
Isabel Age 4/ Daughter
Delancey P.[Pierrepont] Age 2/ Son
Aurelia Segur Age 55/ Servant/ Keeping house/ NY NY NY
Mary Windsor Age 35/ Servant / School teacher/ NY NY NY
Lizzie Barnes Age 40/ Servant/ Servant/ Canada Ireland Ireland
Elize Fleming Age 22/ Servant/ Canada Ireland Canada
Hannah Fleming Age 18/ Servant/ Canada Ireland Canada
Emma Taylor Age 19/ Servant/ New York England New York
Byron Bennet Age 34/ Servant/ NY England England