Maine's eastern boundary is the western edge of the Atlantic ocean

Answer: In this sentence we have subject, verb, subject compliment and prep phrase.

Explanation: I have found that your question is about English grammar.

''I need to identify the subject, verb, and any complements (direct object, indirect object, subject complement, objective complement) and the prepositional phrases of the following sentences.''

Boundary is - subject

is - verb

edge - subject compliment

of the Atlantic ocean - prepositional phrase