In 1867, Charles F. Hoffman of the California Geological Survey conducted the first survey of the valley. Hoffman observed a meadow "well timbered and affording good grazing", and noted the valley had a milder climate than Yosemite Valley, hence the abundance of ponderosa pine and gray pine. The valley was slowly becoming known for its natural beauty, but it was never a popular tourist destination because of extremely poor access and the location of the famous Yosemite Valley just twenty miles to the south. Those who did visit it were enchanted by its scenery, but encountered difficulties with the primitive conditions and, in summertime, swarms of mosquitoes. Albert Bierstadt, Charles Dorman Robinson and William Keith were known for their landscapes that drew tourists to the Hetch Hetchy Valley. Bierstadt described the valley as "smaller than the more famous valley ... but it presents many of the same features in his scenery and is quite as beautiful."