Pinckney’s Treaty with Spain is considered a diplomatic highlight of Washington’s administration because it

This treaty was a diplomatic milestone because it opened up US access to the port of New Orleans.

Explanation:

The Treaty of Pinckney, also known as the Treaty of Madrid, was created to establish a friendly relationship between Spain and the USA, allowing Americans to respect Spanish boundaries and colonies in North America, in addition to allowing both countries to have Mississippi river navigation rights. The great negotiators of these treaties were Thomas Pinckney and Don Manuel de Godoy, the treaty was a milestone in the world history of diplomacy, mainly because it allowed the USA to have access to the port of new orleans.

the answer is b.2008 and 2012 were presidential election years.

answer; /// slavery should be outlawed in the new country, was part of the initial draft of the declaration of independence, but not part of the final