Queen Victoria reigned from 1837 to 1901 and was succeeded by her 60 year old son Edward the Prince of Wales. At the start of the Victorian era, most fashions lasted about a decade, but mass communications and mass production both improved so much that by 1901 the history of fashion was moving in a yearly cycle.
Illustrations of Victorian clothes of the last 20 years of the C19th can be dated to within a year or two. Looking at Crinolines, Bustles and S Bends Corsets would help those new to costume to understand the subtle changes in dress and hairstyles and how to spot the changes from a fashion history point of view.