The painting was last known to be in the Saint Louis area in 1954, when the Society took this photo. According to the record: "William Clark painting owned by Mrs. William Bryce, purchased from the estate of Eleanor Glasgow Voorhis." Also, the Voorhis family apparently had two copies of this painting.
If anyone knows the whereabouts of this portrait, please contact the Missouri Historical Society.
Thanks to Kira Gale.