American poetry refers to the poetry of the United States. It arose first as efforts by American colonists to add their voices to English poetry in the 17th century, well before the constitutional unification of the Thirteen Colonies. Most of the early colonists' work was similar to contemporary English models of poetic form, diction, and theme. However, in the 19th century, an American idiom began to emerge. By the later part of that century, poets like Walt Whitman were winning an enthusiastic audience abroad and had joined the English-language avant-garde.