Steam Era and Empires

An alternate history may or may not be pinned down to a year of real chronology or to a specific real town or country.

Nonetheless, most steampunk writers inform their choices of manners, politics, geography, science, etc with a study of one or more eras. 

If one were to survey the globe from the mid-1800's to the early 1900's, some highlights would include:

Britain
Victorian Era, 1837 - 1901

America
Gold Rush of the 1840's, Gilded Age, and start of Progressive Era

France (and 'the Continent')
La Belle Epoque - end of the Franco-Prussian War to the start of WW I

Japan
late Edo period (to 1868) and Meiji (1868- 1912)

China
late Qing dynasty (1644 to 1911)

India
largely occupied by the East India Company's private army, supplanted by British military in 1857

Middle East
waning decades of the Ottoman Empire