Are you intrigued by the possibilities of what could have been? Alternate history is the genera for you! Alternate history explores America from the perspective of things that could have happened (What would have happened if America lost WWII?) as well more fantastical pasts (What would have happened if there were Zombies in the Civil War?). No matter which direction your curiosity goes, there’s a different America to explore, even if you decide that the one we’re living in right now is just right.
The calculating stars / Mary Robinette Kowal.
On a cold spring night in 1952, a huge meteorite fell to earth and obliterated much of the east coast of the United States, including Washington D.C. The ensuing climate cataclysm will soon render the earth inhospitable for humanity. This looming threat calls for a radically accelerated effort to colonize space, and requires a much larger share of humanity to take part in the process. Elma York’s experience as a WASP pilot and mathematician earns her a place in the International Aerospace Coalition’s attempts to put man on the moon, as a calculator. But with so many skilled and experienced women pilots and scientists involved with the program, it doesn’t take long before Elma begins to wonder why they can’t go into space, too. Elma’s drive to become the first Lady Astronaut is so strong that even the most dearly held conventions of society may not stand a chance against her.
The man in the high castle / Philip K. Dick.
It’s America in 1962. Slavery is legal once again. The few Jews who still survive hide under assumed names. In San Francisco, the I Ching is as common as the Yellow Pages. All because some twenty years earlier the United States lost a war — and is now occupied by Nazi Germany and Japan.
American royals / Katharine McGee.
In an alternate America, princesses Beatrice and Samantha Washington and the two girls wooing their brother, Prince Jefferson, become embroiled in high drama in the most glorious court in the world.
Dread nation : rise up / Justina Ireland.
Jane McKeene was born two days before the dead began to walk the battlefields of Gettysburg. In this new America, safety for all depends on the work of a few, and laws like the Native and Negro Education Act require certain children attend combat schools to learn to put down the dead.
The plot against America / Philip Roth.
When the renowned aviation hero and rabid isolationist Charles A. Lindbergh defeated Franklin Roosevelt by a landslide in the 1940 presidential election, fear invaded every Jewish household in America. Not only had Lindbergh, in a nationwide radio address, publicly blamed the Jews for selfishly pushing America toward a pointless war with Nazi Germany, but, upon taking office as the thirty-third president of the United States, he negotiated a cordial “understanding” with Adolf Hitler, whose conquest of Europe and whose virulent anti-Semitic policies he appeared to accept without difficulty. What followed in America is the historical setting for this startling new book by Pulitzer Prize winner Philip Roth, who recounts what it was like for his Newark family-and for a million such families all over the country-during the menacing years of the Lindbergh presidency, when American citizens who happened to be Jews had every reason to expect the worst.
Coming of age as a free-born Black girl in Reconstruction-era Brooklyn, 
John Sevier had not taken much interest in the American Revolution, because he was too busy fighting Indians in the Carolinas and taming the wilderness. But when an arrogant British officer threatened his settlement—promising to burn the farms and kill families—the war became personal. That arrogant officer is Patrick Ferguson of the British Army—who is both charmingly antagonistic and surprisingly endearing. Inventor of the Ferguson rifle, and the devoted lover to his mistress, Virginia Sal, Patrick becomes 
Scottish prisoner Duncan McCallum, indentured to the Ramsey Company, is troubled by a series of mysterious deaths on the ship carrying him to the New World. When McCallum’s close friend Adam Munroe and a professor who was to work as a tutor are added to the list of the dead, McCallum, who has extensive medical training, is enlisted by the captain to investigate. The shipboard mysteries remain unresolved when they arrive in New York, and McCallum’s quest for the truth leads him to perilous encounters on both sides of the French and Indian War
From his 1776 Pennsylvania homestead, thirteen-year-old Samuel, who is a highly-skilled woodsman, sets out toward New York City to rescue his parents from the band of British soldiers and Indians who kidnapped them after slaughtering most of their community. Includes historical notes.
