In the interest of helping re-enactors and saddle historians place saddle styles in history, I've added a few sketches I made. These sketches represent a generalization of the saddle styles and construction, grouped into ten-year periods. While there is overlap in the stylizations from decade to decade, and I'm not taking into account regionally specific styles, these sketches bring together the most prominent features identifying the most common styles of each ten-year period.
The 1860s Hope Style Stock Saddle developed in Texas from the Mexican Vaquero's Stock Saddle. While Mexican in origins, the Hope shows the influence of Anglo sensibilities and requirements of "Hard-and-Fast" roping practiced in Texas. On the majority of these early saddles, the layers of leather were nailed to the saddle tree, holding them together.
The big breakthrough in saddle technology in the 1870s was the practice of holding the layers of leather together with saddle strings, passing through the layers of saddle construction, rather than nails. This construction technique was a direct result of the long cattle drives beginning towards the end of the Civil War. Cowboys had to be able to repair their saddles along the trail. With long saddle strings holding the saddle together, the saddle could be unlaced, repaired, and laced back together, often using sections of the saddle strings to hold together the repairs.
The 1880s were marked by the widespread use of side jockeys to cover the stirrup leathers, protecting the riders thighs. This required the addition of another set of saddle strings to lace the parts together.
The 1890s marked the end of cattle drives pushing the development of saddle technology. The loop seat allowed for a full seat for the rider, with the stirrup leathers holding down the front of the seat. Adhesives of this era would often loose their grip when they got wet.
At the end of the "Cattle Drive" era, saddle styles and technology became driven by specific "ranch specific" saddle needs. Saddles were developed specifically for roping and branding, cutting and bronc bustin'. No longer did the American Cowboy have to live in his saddle months at a time. It was the end of the era.