Born in Cincinnati, Piatt attended schools in Ohio and began contributing to newspapers as a young man.

[1] In 1827, the family moved to a large home outside West Liberty, Ohio, called Mac-o-chee, later the site of one of the Piatt Castles.

[6] After a visit to Washington, D.C., in late 1841,[7] Piatt began practicing law in Cincinnati in a firm with his brother Wykoff and brother-in-law N. C.

[11] In the late 1850s, Piatt edited and contributed to several newspapers including the small Mac-a-cheek Press, which Donn founded with his brother Abram S.

At some point around June 1863, when Schenck was away from his post attending to business in Boston, Piatt ordered William Birney to recruit a brigade only of enslaved people.

[14] President Abraham Lincoln was going to cashier Piatt for this decision but decided not to after Edwin Stanton and Salmon P. Chase intervened.

[20] In his contributions to Capital, Piatt made fun of clergy including John Philip Newman, critiqued politicians including Zachariah Chandler, mocked John Bingham, and alleged that Vinnie Ream was hired to make statues for her personal beauty and not her artistic talent.

[22] Piatt retired from active work in the newspaper business after a doctor told him his wife's health would improve in a country retreat.

[23] In retirement, he wrote three plays in rapid succession: Lost and Won; A Hunt for an Heiress; and Jane Shore, a King's Love.

[24] In February 1887, he published a collection of newspaper articles about Civil War figures as Memories of the Men Who Saved the Union.

[26] Apparently from Mac-o-chee, Piatt began editing Belford's Monthly, a magazine "embracing a liberal political policy in addition to literary features of the highest excellence", in summer 1887.

[33][1] He died on November 12, 1891, at Mac-o-chee,[1][34] after catching a "severe cold" en route back from a meeting of the Literary Club of Cincinnati.