They apparently settled in Fountain Green Township, Hancock County, Illinois, between 1855 and 1858.

Harriet died on December 12, 1882; John died on July 8, 1899.  Both were buried at Fountain Green Cemetery, as were two of their young daughters.  Based on tombstone inscriptions, John and Harriet lost a daughter named Josephen in 1859.  In 1862 they named their sixth daughter Josephine, and called her Josie.  Josie died in 1879.

Census records do not provide a straightforward accounting of their family; the 1870 listing did not include daughter Nannie, and either Mary Belle or Martha was shown as a 10 year old male.

As best determined, the children of John B. McDonald and Harriet Talbot were:

i.	Franklin Scott McDonald, born about 1849 in Pennsylvania.  He died April 5, 1937, in Hancock County; burial location undetermined.
ii.	Emma Frances McDonald, born about 1851 in Pennsylvania.  On November 6, 1878, she married John Mahannah in Hancock County.  She was about 26, he was about 59, a widower (apparently) with young children.  Marriage documents (100k, 90k) In 1900 John was living in Burlington, Iowa, with his son, Howard.  John was shown as a widower, father of 7 children, 4 living.  In the absence of further evidence, it's not possible to state unequivocally that Emma died; widow or widower was often shown when the true status was divorced or otherwise estranged.  1870, 1880, 1900 Census
iii.	Josephen McDonald, born April 3, 1852, in Pennsylvania, died March 23, 1859, probably in Fountain Green Township.  Burial at Fountain Green Cemetery.
iv.	Nannie E. McDonald, also found as Nancy, born in Pennsylvania in 1855.  She married Michael Huffman Dennison on January 11, 1877, in Hancock County.  Nannie was the last surviving sibling when she died on July 2, 1949.  Interment at Majorville Cemetery, Hancock County, Illinois.
v.	Mary Belle McDonald, born January 19, 1858, in Fountain Green Township.  On November 13, 1879, she married Archibald Dorothy (1851-1882). She later married James Parker Bell, becoming Mary Belle Bell.  She died March 27, 1947, in Augusta, Illinois, and was buried at Moss Ridge Cemetery, Carthage, Hancock County.  Obituaries
vi.	Martha L. McDonald, born in 1860, probably in Fountain Green Township.  On census records her name appears as Mattie, but family members in Kansas called her "Nannie".  She is remembered as being a little woman with a very determined will.  She died June 8, 1945, and was buried at Graceland Cemetery, Meade County, Kansas.
vii.	Josephine (Josie) McDonald, born May 2, 1862*, probably in Fountain Green Township.  She died May 28, 1879, and was buried at Fountain Green Cemetery.
viii.	Grant McDonald, born about 1864, probably in Fountain Green Township.  We have found no record of Grant McDonald after the 1880 Federal Census.
*Birth date calculated from tombstone inscription.

John McDonald, 35, male, farmer, value of real estate 2000, value of personal estate 800,
born PA
Harriet, 28, female, born PA
Scott, 10, male, born PA, attended school within the year
Emily, 8, female, born PA, attended school within the year
Nancy, 4, female, born PA, attended school within the year [??]
Mary [Belle], 2, female, born PA
Martha, 1, female, born PA

McDonald, John, 49, male, white, farmer, value of real estate 1000, born PA, male citizen of the U.S. aged 21 or more
Hattie, 42, female, white, keeping house, born PA
Scott, 21, male, white, help on farm, born PA
Emma, 19, female, white, keepinghouse, born PA
(continued on next page)
McDonald, M, 10, male [sic], white, born IL [no school attendance entry] [perhaps Martha]
Josephine, 8, female, white, born IL [no school attendance entry]
Grant, 6, male, white, born IL [no school attendance entry]

Nannie is missing from this listing.  If the 10 year old "male" was, in fact, Martha, then
Mary Belle is also missing.  This may have simply been an enumerator's transcription error.
Another possiblity is that they were boarding elsewhere while they attended school.

McDonald, John B, white, male, 56, married, farmer, born PA, father born Ireland, mother
born PA
Harriet, white, female, 55, wife, married, keeping house, born PA, both parents born PA
Mattie, white, female, 20, daughter, single, at home, born IL, both parents born PA
Grant, white, male, 16, son, single, at home, born IL, both parents born PA