Crosstime Traffic, Tor, is a six-volume series of alternate history novels aimed at young adults. Set in the late 21st century, the series details the adventures of the employees of Crosstime Traffic, an organization which makes its money by sending traders to various timelines. Each work is set in a different timeline, and effectively acts as a standalone novel. The protagonists in each story are teenagers, usually one boy and one girl, and usually with at least one POV from the home timeline. The six volumes are, in order of publication, Gunpowder Empire, Curious Notions, In High Places, The Disunited States of America, The Gladiator, and The Valley-Westside War.
Sometime in the 21st century, the home timeline (which is probably meant to be our world), having tapped out its resources and facing economic ruin, discovered the secret of traveling across timelines. Through trial and error, it soon becomes clear that there are many alternates where resources are available. A new corporation, Crosstime Traffic is formed for the purpose of setting up trading outposts in various resource-rich alternates, while at the same time preventing the more technologically-advanced alternates from discovering crosstime travel.
While preventing what might have been a terrible collapse of civilization, having access to other timelines did not in itself solve all the problems of the home timeline. The world remained divided into different nation states, and there remained plenty of international tensions and tensions within states, sometimes bursting out into terrible bloodshed. Indeed, crosstime travel itself to some degree contributed to these tensions, due to the feeling that the rich Western countries were getting more than their fair share of the benefits; such feelings were prevalent, for example, in Romania.