Johnson board subscriber, not related.
In reading census Thomas and Susanah went to Kentucky within 10 years or less of their marriage.
The 1800 US Census has the states of CT, DE, D of Columbia, ME, MD, MA, NH, NY, NC, PA, RI, SC and VT.
The 1810 US Federal census is first one that has Kentucky. Thomas, Pleasant and two John Johnson's are enumerated in Clay county.
1820: Absolum, James, John, Robert, Samuel, Thomas and Zachariah Johnson
1830: Herod, 3 James, Jesse, Zachariah, Robert, Samuel, 2 Thomas, William Johnson
1840: Alexander, David, James, Melville, Shadrick, Shedrick and Thomas Johnson.
1850, Clay Co KY
Thomas Johnson, age listed as 78 born VA and Susanah age listed as 68 born MD are enumerated in the 1580 Clay county KY census. Thomas owned land valued at $995.
Their daughter Susan born abt 1819 in KY is listed in their household married to Calvin McLeod born abt 1823 KY. They married 15 Oct 1849 in Manchester, Clay Co.
Calvin is son of Duncan & Barbary McLeod of NC per LDS files.
Also in the household is a Palena/Paulina Hubbard born abt 1837 in KY grand daughter. LDS IGI record shows Palena Hubbard, born 1838 in Clay county to be daughter of Hiram Hubbard/Hibbard and Ann Johnston/Johnson.
Melville/Melvan/Melvin Johnson born 11 Aug 1817 Clay Co KY is listed at next household, wife Julia Ann Henson born abt 1818 and a black male born abt 1843 named Joseph Ambros. No children for Melville and Julia. They married 23 Aug 1838 in Manchester, Clay Co.
Thomas Johnson born abt 1820 in KY, black smith, enumerated in household of W H [Wade Hampton] Walker 1813 KY, merchant, and his wife Frances Ann Baker Walker who was born abt 1823 KY.
Alexander Johnson born abt 1816 in KY, blacksmith, wife America Cain born abt 1820; Josephine abt 1840; Columbus abt 1842; Payten E born abt 1846 and Susan Cain born abt 1833. Alexander married America Cain 14 Apr 1840 Clay County
Benjamin Johnson born abt 1807 in KY, blacksmith, wife Lucinda age 20 or 30 ?; Susan born abt 1845; Mary born abt 1847; male Mell...? possibly Mellville 1850.
James Johnson born abt 1812 in KY, farmer, wife Harriet House Johnson born abt 1825; Julia abt 1840; Jefferson abt 1842; America abt 1845; Alexander abt 1848.
No John or Charles Johnson enumerated in Clay county in 1850. Total of 37 Johnson's enumerated.
Ancestry.com Kentucky marriages 1802 - 1850 has only two marriages in Clay county showing surname of Johnson. Minta Johnson & Robert Morris in 14 Ap 1817 and John Johnson to Nancy Haddix 4 Nov 1822.
21 Jul 1860; Census Place: Not Stated, Clay, Kentucky; Roll: M653_363
Post Office: Manchester
Susan Johnson, age listed as 75, born VA, $100 value of personal estate
Paulina Hebbard, age 22 born in Clay Co
Ann McCrary, age 10 born in Clay Co
Kittie M Hebbard a one month born in Clay Co
Melvill Johnson 40
Julia A Johnson 39
Izabella Gilbert 75 abt 1785 VA
Ellender Mccrary 38 abt 1822 KY, daugther of Thomas and Susanah ?
Julia A Mccrary 1
Ellender McCrary not found in 1850 record. Ann McCrary probably her daughter. Clay county marriages show that an Ellen McCreary married William Whitehead 10 Oct 1861 in Clay county. No female with surname of Whitehead born abt 1822 is found in 1870 census. William Whitehead born abt 1826.
Benja Johnson 49 1811
Lucinda Johnson 32
Susan Johnson 12
Mary Johnson 11
William Johnson 9
Margaret Johnson 6
Thomas Johnson 4
James Johnson 47 1813
Hariet Johnson 38
Thomas J Johnson 17
America J Johnson 15
Alexander Johnson 12 ...possibly in Foxtown, Madison Co KY by 1880
Maria E Johnson 10
Angaline Johnson 7
William L Johnson 3
Leonidus Baker Johnson 3.12
1860; Census Place: Western Subdivision, Madison, Kentucky; Roll: M653_384; Page: 0; Image: 245. Post Office Kirksville
William P Green 31 merchant born Clarke Co KY
Mary F Green 26 born Madison Cty
Gabriller Green 9
Lucy J Green 6
Michael F Green 2
Abner Adams 15
A D Johnson 44 blacksmith, recorded as being born in Madison Co KY
Columbus Johnson 17
Peyton Johnson 15
Name: A. D. JOHNSON
Spouse: MARY FOSTER
Marriage Date: 25 Jun 1861
Name: Mary Foster
Age in 1860: 29
Birth Year: abt 1831
Home in 1860: Western Subdivision, Madison, Kentucky
Post Office: Kirksville
Father: Anderson Foster age 64
Mother: Eliza Foster age 67
Name: COLUMBUS JOHNSON
Spouse: JULIA A. FOSTER
Marriage Date: 26 Jan 1864
Name: COLUMBUS JOHNSON
Spouse: CATHERINE V. WELLS
Marriage Date: 12 May 1875
1870; Census Place: Kirksville, Madison, Kentucky; Roll: M593_484; Page: 186; Image: 378. Post Office: Kirksville
Columba/Columbus Johnson 29 KY
Julia, 24...no Julia A Foster listed in 1860 record born abt 1846
Jaster?, male, 6
Alexander D and Peyton Johnson not found in 1870 record.
1870, Kirksville, Madison, KY, Post Office
Anderson Foster 70
Lizzie/Eliza Foster 70
Eliza Johnson 10
Mollie Johnson 8
Mary Johnson 40...appears to be widow of Alexander D Johnson
1870; Census Place: Precinct 1, Clay, Kentucky; Roll: M593_456; Page: 145; Image: 291. Post Office Manchester
Melvill Johnson age 53
Julia Johnson age 51
Ann McRary age 15
George McRary age 10
1870, Laomi, Sangamon, IL
Calvin B Mcloyd 1823 NC
Susan Mcloyd 1820 KY
Maria L Mcloyd 1853 KY
William H Mcloyd 1856 KY
Anna Mcloyd 1858 KY
1880; Census Place: Manchester, Clay, Kentucky; Roll: T9_410; Family History Film: 1254410; Page: 467.2000; Enumeration District: 22; Image: 0138.
Melville Johnson, age 62, born KY 1818, parents listed as VA, occupation: Magistrate
Julia Johnson, age 61, KY NJ PA
Sarah Jewel, age 14, KY white female, listed occupation is "bound"
1880: Beattie, Marshall, KS
D L McLeod, age 59, born NC
Susan McLeod, age 59, born KY, father VA, mother MD
William McLeod, age 24, born KY son
Anna McLeod, age 21, born KY dtr
1880: Kirksville, Madison, KY
Anderson FOSTER Self W Male W 83 VA House Carpenter VA VA
Mary JOHNSON Dau Widow Female W 49 KY Keeping House VA VA
Mollie JOHNSON GDau S Female W 16 KY Seamstress KY KY
Lucy JOHNSON GDau S Female W 10 KY At Home KY KY
Alexander JOHNSON GSon S Male W 7 KY KY KY
Anderson JOHNSON GSon S Male W 15 KY Farm Laborer KY KY
Elizabeth JOHNSON GDau S Female W 13 KY Domestic Servant KY KY
Charles JOHNSON GSon S Male W 1M KY KY KY
I can not begin to explain who all of these Johnson's are. Anderson Johnson married Allie Peters, 6 Nov 1890 in Madison Co. I did not find a Anderson Johnson in the 1870 Madison county census.
Well...this will give you a place to start. Good Luck !