“Old Amos,” as he was known, was the grandson of a man who had been caught as a young boy by slave traders on the coast of Africa; he was brought to Springfield, Massachusetts, and later successfully sued for his freedom.
Amos worked for the Dickinson family for at least 8 years, and in 1851, Dickinson wrote of “Old Amos” in a letter to her brother Austin: “The garden is amazing - we have beets and beans, have had splendid potatoes for three weeks now. Old Amos weeds and hoes and has an oversight of all thoughtless vegetables. The apples are fine and large in spite of my impression that Father called them ‘small.’"
Amos died at age 84 in 1859 – and, if Dickinson did write “Went up a year this evening” in tribute to him, then perhaps the poem is misdated?
When exploring this poem, I found an interesting interactive site – a virtual walking tour of Black Amherst called “Reorienting Dickinson,” HERE. "Old Amos” is mentioned at sites 2, “West Cemetery,” and 9, “Newport House.”