Task: Question Answering
Input (English): Passage: Forty-eight Non-Indian people visited Yosemite Valley in 1855, including San Francisco writer James Mason Hutchings and artist Thomas Ayres. Hutchings wrote an article about his experience that was published in the July 12, 1855, issue of the Mariposa Gazette and Ayres' sketch of Yosemite Falls was published in late 1855; four of his drawings were presented in the lead article of the July 1856 and initial issue of Hutchings' Illustrated California Magazine. The article and illustrations created tourist interest in Yosemite and eventually led to its protection.Ayres returned in 1856 and visited Tuolumne Meadows in the area's high country. His highly detailed angularly exaggerated artwork and his written accounts were distributed nationally and an art exhibition of his drawings was held in New York City.
Hutchings took photographer Charles Leander Weed to Yosemite Valley in 1859; Weed took the first photographs of the valley's features, which were presented to the public in a September exhibition held in San Francisco. Hutchings published four installments of "The Great Yo-semite Valley" from October 1859 to March 1860 in his magazine and re-published a collection of these articles in his Scenes of Wonder and Curiosity in California, which remained in print into the 1870s.
Carleton Watkins exhibited his 17 by 22 in (43 by 56 cm) Yosemite views at the 1867 Paris International Exposition.Photographer Ansel Adams made his first trip to Yosemite in 1916; his photographs of the valley made him famous in the 1920s and 1930s. Adams willed the originals of his Yosemite photos to the Yosemite Park Association, and visitors can still buy direct prints from his original negatives. The studio in which the prints are sold was established in 1902 by artist Harry Cassie Best.Milton and Houston Mann opened a toll road to Yosemite Valley in 1856, up the South Fork of the Merced River. They charged the then considerable sum of two dollars per person until the road was bought by Mariposa County, after which it became free.
In 1856, settler Galen Clark discovered the Mariposa Grove of giant sequoia at Wawona, an indigenous encampment in what is now the southwestern part of the park. Clark completed a bridge over the South Fork of the Merced River in 1857 at Wawona for traffic headed toward Yosemite Valley and provided a way station for travelers on the road the Mann brothers built to the valley.Simple lodgings, later called the Lower Hotel, were completed soon afterward; the Upper Hotel, later renamed Hutchings House and eventually known as Cedar Cottage, was opened in 1859. In 1876, the more substantial Wawona Hotel was built to serve tourists visiting the nearby grove of big trees and those on their way to Yosemite Valley. Aaron Harris opened the first campground business in Yosemite in 1876. 
Question: What are the first names of the two Mann brothers who charged a considerable sum of two dollars per person for access to their toll road until it was purchased by Mariposa County?
Output (English): Houston.