Boulder Dam was the original name for Hoover Dam.

The phrase is for hoover Dam.
Is it an adjective or an adverb phrase?

What is it describing?

original name right?

Yes ... so it's __________________.

An adjective phrase

yes

In order to determine whether the phrase "for Hoover Dam" is an adjective or an adverb phrase, let's break it down and analyze its function in the sentence.

The word "for" is a preposition, and in this context, it indicates the purpose or destination of an action.

The noun phrase "Hoover Dam" refers to a specific dam, which is the subject of the sentence.

When we look at the phrase as a whole, "for Hoover Dam" describes the purpose or destination of the action. This suggests that it is functioning as an adverbial phrase modifying the verb or the action in the sentence.

Therefore, "for Hoover Dam" is an adverbial phrase. It provides additional information about the purpose or destination of the action.