From the US Federal Census Records on Edward Clark.

Unfortunately the enumerators only used initials for most of these records; which they were not supposed to do.

17 Sept 1850; Marshall, Harrison, TX
E. Clark, 32, lawyer, born LA
M. H.? Clark, female, 21, born TN
William E Clark, male, 1 month?, born TN?
M. H. Clark, female, 62, born GA
G. E. Taylor, female, 16, born SC
G. Taylor, female, 14, born SC

2 Aug 1860; TEXAS, TRAVIS, AUSTIN
Series: M653 Roll: 1306 Page: 271
E. Clark, male, 42, born LA, Lt. Governor, $3000 real estate $10,240 personal estate.
M. M. Clark, female, 31, born TN
John Clark, 8, born TX
W. E. A. Clark, male, 7, born TX
N. M. Clark, female, 5, born TX
M. H. Clark, female, 76, widow, born VA

The Clark family is not found in the 1870 record.

Year: 1880; Census Place: Marshall, Harrison, Texas; Roll: T9_1309; Family History Film: 1255309; Page: 328A; Enumeration District: 41; Image: 528.
J. E. Clark, 28, TX LA TN
N. M. Clark, sister, 25, TX LA TN
M. M. Clark, mother, 51, widow, TN -- --

The 1900 record is only year in which the inhabitants were asked in which month and year they were born. It also asks length of marriage and how many children had been born and living to this union.

John Clark owned his home on N. Franklin Street.

4 June 1900; TEXAS, HARRISON, 3-WD MARSHALL, 407 N Franklin St.
Series: T623 Roll: 1643 Page: 205 ED: 47 Sheet 4B
John Clark, head of household, 1/1852, 48, married 6 yrs, b. TX, father listed as GA, mother TN, bookkeeper.
Juanita Clark, wife, 1/1870, 30, 4 children born and living, TX GA TN
John M Clark, son, 5/1894, 6
Edward Clark, son, 6/1895, 4
Margaret Clark, dtr, 10/1897, 2
Hartsill Clark, son, 3/1899, 1
Patsy A or K Clark, dtr, 3/1888, 11

This is John Clark's second marriage and Patsy Clark is not the dtr of Juanita.

15 Apr 1910; TEXAS, HARRISON, 3-WD MARSHALL, 407 N Franklin St.
Series: T624 Roll: 1562 Page: 165 ED: 49 Sheet 6B
John E Clark, 57, married twice, 17 years current marriage, b. TX, this time parents are listed as GA, bookkeeper for wholesale grocery.
Juanita H Clark, 40, 4 children born, 3 children living, TN AL TN
John M Clark, 15
Margaret K or R Clark, 12
Oliver Hartsill Clark, 10
Patsy K Clark, 20, teaching public school.
Bettie M Miller, 52, single, sister in law, TX AL TN.

Edward Clark died between 1900 and 1910.

14 Jan 1920; TEXAS, HARRISON, MARSHALL, 407 N Franklin St.
Series: T625 Roll: 1815 Page: 181 ED: 57 Sheet 11A
John Clark, listed as 60 yrs of age, bookkeeper for retail grocery.
Juanita Clark, 50
Patsy Clark, 30, single, school teacher
Margaret Clark, 21, single, school teacher
Heartsill Clark, 20, bookkeeper at bank
Belle Miller, 60, sister in law.

4 Apr 1930; TEXAS, HARRISON, 4-WD MARSHALL, 407 N Franlin St.
Series: T626 Roll: 2354 Page: 146
Juanita Clark, 61, widow
Heartsill Clark, 30, single, cashier at 1st Nat'l Bank
Belle Miller, listed as 43 yrs of age
and 4 borders who were public school teachers.

Whereabouts of eldest son John M Clark not known.

Harrison County Genealogical website on Texas GenWeb
http://www.txgenes.com/TxHarrison/

Marshall Cemetery

Clark, Edward Mexican American and Civil War Governor of TX 1861
b. Apr. 1, 1815 d. May. 4, 1880

Clark, Margaret H. Mother of Governor Edward Clark
b. Mar. 18, 1785 d. Mar. 9, 1873

Clark, W. E. A. Son of Edward & M.M. Clark
b. Jul. 12, 1853 d. Apr. 9, 1879

There are photos of Edward Clark's headstones on this link. One is confederate marker indicating he was member of the 14th Texas Infantry, CSA.

Jan Craven's Scrapbook of Harrison County Marriages and Deaths - 1870 to 1901
John Clark married Leila Price ....sometime in mid 1880's?

Historical Markers & Landmarks
Marker Title: Governor Edward Clark
Address:
City: Marshall
County: Harrison
Year Marker Erected: 1963
Designations: na
Marker Location: Courthouse lawn, Houston at Washington
Marker Text: (1815-1880) Born in Georgia. Came to Texas in 1842. Served as a member of Annexation Convention. 1st and 2nd Texas Legislatures. Hometown Texas First Confederate Governor Son of a Georgia governor. Participant Mexican War. Secretary of State 1853-7. Elected Lieutenant Governor 1859. Made Governor 1861 upon removal of Gov. Sam Houston, who opposed secession. Clark's major activity was mobilizing Texas in cause of Confederacy. Plans were made to prevent Federal invasion, take over enemy property, organize resources to provide supplies and arms for defense, and to properly care for families of Texas soldiers battling at the front. Gov. Edward Clark's term from March to November 1861 also faced difficulties caused by mechanics of changing flags, seals, currency, postal and tax systems for membership in new nation. Camps of instruction were set-up over state to enroll, equip and train troops. Hardest job was to convince Texans, the best horsemen in world, that all could not ride in cavalry but some must be foot soldiers in infantry. The C.S.A. was supplied guns, powder, lead, cloth made in penitentiary, salt and 20,000 troops in his term. In late 1861 he raised and became colonel 14th Tex. Inf. Regt. Led units in Arkansas-Louisiana campaigns to prevent invasion of Texas. Wounded and commended Battle Pleasant Hill April 1864. Discharged 1865. Postwar lawyer, businessman. Buried in Marshall
Cemetery.

Special transcribed Projects
http://www.rootsweb.com/~usgenweb/tx/txsearch.html

You can link to the above website which has birth, marriage and death records. Birth record through 1949 include parents names from which you can try to find if Heartsill Clark ever married and had children.