When Miller received his request from Walters for two hundred watercolors, he drew extensively from existing compositions created in the field or for Sir William Drummond Stewart. However, he still needed to conceive a number of new compositions to fill out the commission. Big Sandy/Green River appears to be one such sketch.
The image shows an everyday scene of two trappers on horseback conversing, one gesturing with his crop while two others on the ground gather wood and make a fire for camp. Since Miller was not out West during the trapping season, he would not have had an opportunity to follow trappers or see their encampments. His own experience traveling with Stewart, however, including their jaunt with a smaller party up in the Wind River Mountains following the rendezvous, would have provided the imagery for this sketch.
The overall composition, as well as the style in which he rendered Big Sandy/Green River and the finished watercolor Trapper’s Encampment on the “Big Sandy” River (The Walters Art Museum, CR# 286A), suggest these images were painted very close together in time. Miller’s handling of the branches and leaves of the tree on the embankment, as well as its exposed roots, are very similar. Likewise Miller’s choice of a gray blue tonality for the water and sweeping strokes of umber and buff to render the embankment is the same in each image.