The westernmost point in the USA is on Amatignak Island, in the Aleutian Islands – part of Alaska. Its longitude is a fraction over 179 degrees west. The westernmost point of the US mainland – also in Alaska – is at just over 168 degrees west.
Hawaii is the next most westerly state; its westernmost point is at a little under 157 degrees west.
The identity of the easternmost point of the USA is something of a trick question; it's on Semisopochnoi Island, also in the Aleutian Islands – immediately west of Amatignak, in fact (as it would be) – just the other side of the 180 degree longitude. Its longitude is a tad over 179 degrees and 36 minutes east.
The American Aleutian Islands extend to about 173 degrees east. There's then a gap to the Commander Islands – the geographical extremity of the chain – at about 167 degrees east. These belong to Russia, and are between approximately 120 and 200 miles off the Kamchatka peninsula.
The USA's southernmost state is Hawaii, and its capital – Honolulu – is the most westerly state capital, at just under 157 degrees west. Juneau, the capital of Alaska, is at just under 135 degrees west.
Juneau is in the Alaskan 'panhandle', which runs down the Pacific coast and is bordered to the north–east by British Columbia (Canada). The border between Alaska and Yukon Territory (Canada) is at 141 degrees west.
© Haydn Thompson 2019