Jacobs was first licensed to preach by the Charleston Presbytery in April 1863 and was made pastor of three churches in Clinton shortly following his graduation from Columbia Theological Seminary in May 1864.

[4][1] Aged 17, Jacobs was in attendance when the South Carolina General Assembly voted in convention to secede from the United States on December 20, 1860.

[5] He was a supporter of secession, and he wrote in his diary that David Flavel Jamison's declaration of South Carolina as an independent nation "was the noblest moment of my life".

[16] Jacobs was made chairman of the Clinton Male Academy board of trustees by February 1866[17] and received an honorary Master of Arts degree from the College of Charleston in March 1867.

[18] He declined offers to preach in Albany, Georgia, in March 1868,[19] and in Good Hope, Alabama, in November 1871.

[20] By December 1868, he had ceased preaching at Duncan's Creek and Shady Grove and was working solely at First Presbyterian Church in Clinton.

[30] Construction on the orphanage continued throughout the rest of the year, and in January 1875 a date of October 1 was set as a target for its opening.

[31] The target was met, and Thornwell opened on October 1, 1875, housing ten orphan children.

[38] On September 11, 1880, Jacobs directed William States Lee, the principal of Clinton High School, to "organize the first of his college classes".

[46] The college's third president, Joseph Whitner Kennedy, died in February 1891 and was replaced on an interim basis by John Irvin Cleland, who was one of four members of the faculty.

[1] Their son Thornwell Jacobs was president of Oglethorpe University from 1913 to 1941 and contributed to their Crypt of Civilization.

[59] Jacobs was an advocate for the temperance movement,[36] and he authored a bill in February 1878 to outlaw the sale or manufacturing of alcohol in Clinton, which passed the legislature and was signed into law several weeks later.

[63][52] He was not sick around the time of his death and had only begun to complain of a headache that morning; he was found unconscious shortly afterward.

[64] His funeral was scheduled for September 12, with Davison McDowell Douglas, the president of Presbyterian College, leading the service.

At Presbyterian College, Jacobs Hall was constructed in 1915 and housed an auditorium, library, and laboratory space.

[66] Jacobs was referred to by many of his obituaries as the "Father of Clinton",[67][52][68][69] and The Greenville News called him "one of the grand old men of South Carolina".