Congress was buying art at upwards of $10k in the late 1800s. Moran, specifically sold two paintings to congress for $10k each in 1873. That's a lot of money by todays standards. A couple of inflation calculators equate that to having the same buying power as $230k dollars in 2012. Kind of, i can't find a calculator that will take me back any further than 1914. If the adjustments for inflation are accurate Moran made close to half a million for two paintings. http://www.bls.gov/data/inflation_calculator.htm
His connection to congress was made through this work on the yellowstone region.
Thomas Moran's vision of the Western landscape was critical to the creation of Yellowstone National Park. In 1871 Dr. Ferdinand Hayden, director of the United States Geological Survey, invited Moran, at the request of American financier Jay Cooke, to join Hayden and his expedition team into the unknown Yellowstone region. Hayden was just to embark on his arduous journey when he received a letter from Cooke presenting Moran as.. "an artist of Philadelphia of rare genius.." Funded by Cooke (the director of the Northern Pacific Railroad), and Scribner's Monthly, a new illustrated magazine, Moran agreed to join the survey team of the Hayden Geological Survey of 1871 in their exploration of the Yellowstone region. During forty days in the wilderness area, Moran visually documented over 30 different sites and produced a diary of the expedition's progress and daily activities. His sketches, along with photographs produced by survey member William Henry Jackson, captured the nation's attention and helped inspire Congress to establish the Yellowstone region as the first national park in 1872. The paintings of Moran along with the photographs of Jackson revealed the scale and splendor of the beautiful Yellowstone region more than written or oral descriptions, persuading President Grant and the US Congress that Yellowstone was to be preserved. Naturally proud of the role he played, Moran adopted a new signature: T-Y-M, Thomas "Yellowstone" Moran thereafter. From Wikipedia
Congress was buying art and they were paying good money for it...