Answer:
Free verse .
Step-by-step explanation:
Free verse is the form of poetry writing where there are no specific rules or structures, be it rhythm or meter or even rhyming scheme used. It is the form of poetry where the poem is written in an open form, however, the poet feels like.
The poem "Lincoln Looked" is written in open verse with no rhyme scheme. It also has no rhythm, no specific structure nor any form. Therefore, the structure of the poem is free verse.