His WWI draft registration card, issued in 1917/1918 (the images on Ancestry do not show the side of the card that has the date it was filed), says Johnie Dehart, age 25, residence Hilda, Ky, born 29 Sep 1891 in Elliott Co., occupation farming, married with wife and one child.

In all records from the 1910 census onward, her name appears as Isa, Icy, Icie or some variant, with ages suggesting a birth in 1900. But the 1900 census for George and Linda records a daughter Lena, age 1/12, born May 1900. It is possible that the daughter Lena died young, and that Isa was born in 1901, but if so, it would mean that she was married at age 13 instead of 14. So I think it more likely that Isa is the daughter born in May 1900, and that George and Linda changed their minds about what to call her after the 1900 census was taken.

Rowan Co. marriage book 9, p. 26, records the marriage on 13 Oct 1914 of John Dehart, 22, residence Hilda, born Elliott Co., son of George R. & Julia Dehart, to Icy Hall, 14, residence Hilda, born Rowan Co., dau of G. M. & Linda Hall, at Hilda, Ky, by G. W. Hardeman, Methodist minister, witnesses Abe McClurg & John Stone.

1920 census of Rowan Co., Ky, Morehead precinct, enumerated 10 Jan, lists on p. 5B as family #97/103:
DeHart, John, 27, b. Ky Va Ky, driver for livery stable; Icy, wife, 19, b. Ky Ky Ky; John S., son, 3, b. Ky Ky Ky.