Young John J. Jackson Jr. received a private education near home, then traveled north to attend the College of New Jersey (now Princeton University), from which he graduated in 1845.

Probably Jackson continued to reside at home (Parkersburg being the Wood county seat), helped his father attend the family's considerable business interests, and only traveled to the outlying counties when court was in session.

[2] Jackson Jr. was appointed the Commonwealth attorney for Wood County and served from 1850 to 1851, when the post became elective under the new state constitution.

After leaving the legislature as 1855 closed, Jackson Jr. concentrated on his family's real estate and other business interests (which boomed after the discovery of oil at Burning Spring in Wirt County), as well as his private legal practice in Parkersburg until 1861.

[3][4] On July 26, 1861, President Abraham Lincoln nominated Jackson to a seat on the United States District Court for the Western District of Virginia vacated by Judge John White Brockenbrough, who had sided with Virginia's secessionists.

Meanwhile, the United States Senate confirmed Judge Jackson Jr's appointment on August 3, 1861, and he received his commission the same day.

[3] It has been said that Mother Jones, while under trial for actions related to organizing a coal miner's union, claimed that Jackson had stolen his position as judge from his father, who had the same name.