The letter, sent form Cincinnati, Ohio gave details to his father about his current trip to Washington, D.C., to meet Spencer Baird

The letter, sent from the Smithsonian institution, discussed Ridgway's upcoming meeting with Clarence King, in New York City, his trip west to San Francisco on the steamship "Henry Chauncey", and his ornithological work at the Smithsonian.

The letter detailed to Robert's father what kind of equipment he had been outfitted with for the U.S.G.S. expedition.

The letter mailed from the steamer "Chauncey" at sea in the Caribbean told his father about his travels in the Caribbean and in the Panama area, with specific attention given to the flora and fauna of the areas

This letter again described to his father his travels through Panama and into the Pacific Ocean. It was mailed from the steamer "Constitution" at sea off of the coast of Oaxaca, Mexico

This letter, titled Sacramento, California, Camp no. 1, U.S.G.S. described to his mother the establishment of the survey party's first camp. A second letter is torn in half with no date and no addressee. It was most likely sent to Harriet Ridgway, as the contents mention the word mother. The letter was postmarked by Ridgway's hand, from Carson City, Nevada and includes several hand drawn bird stamps

This letter was sent from Camp #12 at Big Bend of Truckee, Nevada. The letter described to his mother his trip from Sacramento, California through the Sierra Nevada mountain range, into Nevada. Of particular interest was his description of Chinese railroad workers blasting granite on the Central Pacific railroad grade. He finishes with an outline of his upcoming trip to Pyramid Lake, Nevada

This letter was sent from Camp #17, "Banks of the Humboldt River," and it described, to his father, his trip with Mr. Parker (an Indian agent) and Mr. O'Sullivan (the U.S.G.S. photographer) to Pyramid Lake, Nevada. Part of this letter is missing

This letter was sent from "Camp #19 Buena Vista" and discussed his summer's field work. Of particular interest in this letter was a list of Piute Indian names for birds and simple expressions that Ridgway has put together

This letter was sent from "Headquarters U.S. Geological Exploration 40th Parallel", Carson City, Nevada and detailed photographs that he had sent home with the letter. These photographs were not in this collection