From the introduction:
Savage Sidewinder focuses on the Old West during the 19th century on the North American continent. As such, it is best described as a “traditional Western,” set against the historical backdrop of westward expansion in the USA. This core book provides ideas and guidelines for running a game in either of two time periods during the 19th century: 1804–1848 or 1849–1899.
The Savage Sidewinder core book provides historical background for playing games in both eras, with suggestions for game mechanics and role-playing flavor influenced by the historical events during each period. This book offers general commentary, new Setting Rules, time-specific Gear, and character design ideas for time periods during the 19th century in North America.