Final answer:
The state that includes the Atlantic Ocean, and Long Island, and extends from New York Harbor to Montauk Point is New York. Long Island is an essential part of New York's geography with historical and economic significance.
Step-by-step explanation:
The state that has the Atlantic Ocean, Long Island, the longest island in the 48 contiguous states, and extends from New York harbor to Montauk Point is New York. Long Island is an integral part of New York State, which played a significant historical role in battles such as the one at Brooklyn Heights on August 27, 1776.
The geography along the Atlantic coast features various landscapes, with regions like Long Island having a steeper geography compared to the gently sloping nature of the southeastern coastlines.
The strategic importance of Long Island and New York City has been highlighted throughout history for its advantages in transportation and commerce, such as the opening of the Erie Canal in 1825 that substantially boosted New York City's growth by connecting the Great Lakes to the Atlantic. Nowadays, New York City is the largest city in the United States due to these and other historical developments.