Alaska is a state of the United States. It is by far the largest state by geographical area, but is also not part of the Contiguous United States, instead located further northwest on a peninsula of the North American continent bordering the Pacific Ocean to the south, the Arctic Ocean to the north, Canada to the east, and the Russian Far East on the continent of Asia to the west just across the Bering Strait that connects the Pacific with the Arctic. Despite its massive area, Alaska is actually the third least populous state, with only Vermont and Wyoming having fewer residents; indeed, the vast majority of Alaska is open undeveloped wilderness with very few people. The state straddles the Arctic and is often associated with it, but its Pacific coast regions are actually very temperate with mild winters.
In Tales of the TMNT Volume 2, issue #27: White Horses, April O'Neil travels alone to the Alexander Archipelago off the coast of the Alaska Panhandle in the state's southeast. Having recently learnt that she was drawn by her father and was never human to begin with (which is also why she cannot conceive her husband's children), she is having an existential crisis, and has traveled to Kruzof Island, passing through the town of Sitka on the way. On Kruzof, April meets Onida, an elderly Tlingit woman. April and Onida bond in this remote place, and April confesses the real reason she has come here: to die. Onida tells April that living or dying are choices. Later, April encounters and is attacked by a bear guarding its cubs, and she nearly falls off a steep cliff trying to get away. Why hanging from an outcrop, she thinks of her recently deceased second father Splinter, wondering if her death too is imminent. But Onida appears at the top of the cliff, asking April if she wants to choose to live. After April chooses life and safely leaves Kruzof behind, it is shown that Onida is actually the spirit of a white horse who is grateful that April will live to remember her.
In the IDW continuity, Alaska is Alopex's birthplace, where she was captured as an ordinary arctic fox pup and mutated at an Alaska-based laboratory associated with the Foot Clan. After Alopex escapes from Kitsune's psychic mind control in Fox Hunt, part 2, she returns to Alaska in Desperate Measures: Prologue, where Raphael and Angel Bridge also travel to reunite with her.