— born in Tazewell Co., IL:
5.  Agnes B? CORNELIUS, b. 1836/7; d. by 1887
6.  Lynn/Lym B. CORNELIUS, b. 1837/8
7.  Jesse CORNELIUS, b. 1839/40; d. by 1887
8.  Mary Elizabeth CORNELIUS, b. 1840/1
9.  Levi CORNELIUS, b. 1841/2

1a.  Jordan R. Dodd, ed.  1993.  Kentucky Marriages:  Early to 1850.  Liahona Research, Orem, UT (Broderbund CD-229):

Cornelius, Henry P.

Quisenberry, Mary

17 Jul 1828

Christian Co.

1b.  Illinois Statewide Marriage Index, 1763–1900:

Cornelius, Henry P

Quisenberry, Catharine

McLean Co.

29 Jul 1847

Book B

p. 161

2.  Census Index:  U.S. Selected Counties, 1830 (Broderbund CD-315):  can't find.

3.  Census Index:  U.S. Selected Counties, 1840 (Broderbund CD-316):  can't find.

4.  1850 Census Index/Images (online at Ancestry.com; Image #260 of 290):  Tazewell Co., IL, p. 129B, 1783/1783, enumerated 17 Dec 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Henry Cornelius	44	M		Farmer	3000	Ky
Catheran   "	22	F				Ky
John H     "	21	M				Ky
Edward     "	20	M				Ky
Nancy Ann  "	18	F				Ky
Wistons?   "	15	M		Farmer		Ky
Agness B   "	13	F				Ky
Lym/Lynn B "	12	M				Ills
Jessee     "	10	M				Ills
Elizabith  "	9	F				Ills
Levi       "	8	M				Ills
Ann        "	3	F				Ills
Edward Corkolng?	30	M				Va

5.  AIS (Accelerated Index System) 1860 Census Index (online at Ancestry.com):  not found, but Tazewell Co., IL, records are not indexed in this database.

6.  1870

7.  1880

8.  1890 Census:  the 1890 census population schedules were destroyed.

.  Anon.  1887.  Portrait and Biographical Album of Champaign County, Ill.  Chapman Bros., Chicago, IL.

Henry P. Cornelius ... lives in Brown Township, where he is the proprietor of a good homestead on section 16 and employs the greater part of this time superintending the cultivation of 160 acres of improved land.  He took up his abode here in 1882 ...  Mr. Cornelius was born within seven miles of Hopkinsville, Christian County, Kentucky, March 16, 1806, and is the son of John and Martha (Profitt) Cornelius, the former a native of North Carolina, and the latter of Virginia.  After marriage, they commenced life together in Christian County, Kentucky, where they reared a family and spent the remainder of their days.  The children of the parental family who grew up on the farm in the above county were eight, four of whom are now living.  The subject of our sketch removed to Tazewell County, Illinois, in 1836 and lived there over forty-five years.  He first located in Hittle's Grove Township, where he lived until the spring of 1877, and from there removed to Minier, where he lived five years, and thence removed to Brown Township, this county, locating upon his present farm.  Mr. Cornelius was first married, in his native county in Kentucky, July 17, 1828, to Miss Mary Quisenberry, who was of Southern birth and parentage, her father and mother being natives of Virginia, of which she was also a native.  Of this marriage there were born nine children, whom they named as follows:  John H., Edward, deceased, Nancy A., Gustavus, deceased, Agnes, deceased, Lin, Jesse, deceased, Mary and Levi.  The wife and mother, while the famliy were living in Hittle's Grove Township, folded her hands for her final rest in 1845.  The second wife of our subject to whom he married in McLean County, Illinois, in July 1847 was Miss Catherine Quisenberry, also, a native of Christian County, Kentucky, born July 20, 1826.  Mrs. Catherine Cornelius became the mother of eight children, all of whom are living, namely, Ann, James, Charles, Millard, Laura, George M., Ida and Julia.  Mr. Cornelius is greatly opposed to the manufacture and sale of spiritous liquors and in voting upholds the principles of the Republican party.