He enlisted in Company C, 1st Florida Reserves Infantry 2 May 1864, and was discharged at Madison, Florida on 12 May 1865.
(NARA PUB M #251 REEL #32)

The info below is given without any documentation and this is the reason I do not make edits that are not proven to be correct.
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Info below from: Beals (#46830236)
James Dallas Johnson was the son of Alexander Johnson and Mary Pynes. He married Julia Stephens and they were parents of Minnie Lee (Oswald), Ida Jane, James Alexander, and Daniel James Johnson. James and Julia are at rest in Bascom Cemetery.

Note: Daniel Pynes will is documentation that his daughter Mary Pynes was married to Alexander Johnson. James was their son. Please let me know if you need further documentation. I have a copy of Daniel's will.
Pynes, Daniel 1831-1854 There is an estate case for a Daniel Pynes dated 1831-1854.
Executor: Hamilton F. Dees and James Pynes
Executrix: Rutha Pynes
Heirs:
James Pynes
White Pynes
Benjamin Pynes
Mary Pynes wife of Alexander Johnson
Children of Fair Pynes deceased
Children of Nancy Dees deceased Henry County Estate Case Files.

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Info below from: R Watson (#47489987)
RE: James Dallas Johnson - Memorial #3004582
Hi Winnette - The Father listed on this Memorial Appears to be incorrect and conflicts with the information given in the bio. James D. Johnson appears with the parents listed in the bio on the 1850 in Jackson County, Florida. Their father appears is found living with his daughter Ruthay Johnson Stephens and her husband, John T. Stephens on the 1880 Census. Do you have any information about Albert Johnson that would suggest he is the same person as Alexander Johnson or that the father of James Dallas Johnson is Albert and not Alexander?