Day was born at Granville, Washington County, New York, and attended common schools.

His father died when Luther was twelve, and he worked until age twenty to support the family at a farm and sawmill.

[1] He moved to Ravenna, Portage County, Ohio, studied law under Rufus P. Spalding, and was admitted to the bar October 8, 1840.

[2] In 1843, Day was elected Prosecuting Attorney of Portage County but moved to Akron in 1845 for about a year.

[3] Day resigned his Senate seat because he was elected a judge on the Ohio Supreme Court in 1864.