On February 8th, 1882, Wilde lectured in Buffalo, NY. It was his twelfth lecture of the tour overall, but his seventh in nine days and he was beginning to weary of the travel.
"But I’m dreadfully tired...it isn’t the lecturing. I delight in giving my lectures when I find there is interest in them, but it’s the long distances. The traveling has nearly used me up. I haven’t been used to it you know. At home I’d get up in the morning, have breakfast, do some writing, and then maybe start off for Egypt or some other distant port, but take my time about it all." 
Fortunately for Wilde the Buffalo lecture was a rare matinee, and there was time for him to take a much needed break with a visit to Niagara Falls. So he 'courteously' declined social invitations for the evening, and boarded the 6:10 PM train over the Central Railroad to Niagara Falls, some twenty miles to the north of Buffalo.
Today there are twin cities of Niagara Falls.
One is in the state of New York, but this one had not yet been incorporated at the time of Wilde's visit . The other is in Ontario on the Canadian side . This is the one Wilde visited and he put up at Prospect House .
Since Wilde's arrival in New York for his tour of America, much had been made in the press of his remark that he was disappointed in the Atlantic Ocean. Now at Niagara Falls, Wilde was confronted by another majestic embodiment of the natural world, and was again moved to apparent meiosis.
"When I first saw Niagara falls I was disappointed in the outline. The design, it seemed to me, was wanting in grandeur and variety of line, but the colors were beautiful." 
Verses from British satirical periodical Fun.
Prospect House, Niagara Falls, ON (1880)
Location of Prospect House marked at the foot of the map close to the falls.
New York Herald, October 30th, 1882, 5
From the notes in: Decorative art in America: a lecture, Together With Letters, Reviews and Interviews, Edited With an By Richard Butler Glaenzer, p. 243. (Brentano's 1906)
 Buffalo Express, February 9th, 1882.
 The City of Niagara Falls, NY was incorporated on March 17, 1892 from the villages of Manchester and Suspension Bridge, which were parts of the Town of Niagara in the southwest corner of the county, a settlement originally founded in 1812 as the "Town of Schlosser". (Wikipedia)
 In 1882 the city of Niagara Falls, ON had only recently adopted that name. In 1856, the town of Clifton was incorporated and changed its name to Niagara Falls in 1881. In 1882, the community of Drummondville (located near the present day corner of Lundy's Lane and Main Street) incorporated itself as the village of Niagara Falls. Thus there were two municipalities named Niagara Falls at the time (with the village being referred to as Niagara Falls South to differentiate it from the town). In 1904, the town and village finally amalgamated to form the City of Niagara Falls. (Wikipedia)
 There were other hotels known as Prospect House in the area before and after this one, the name presumably popular because of the view afforded of the Falls from the now collapsed plateau of Table Rock.
 Buffalo Express, February 10th, 1882.
Oscar Wilde, in the Prospect House album, 1882