Most contemporary reports of Wilde's lecture in Lincoln, Nebraska on April 24, 1882 name City Hall as the location for his lecture; one other report says he lectured at the opera house. Neither of these is entirely wrong, but neither alone allows us to be definitive.
The two venues immediately suggested by those references are:
1) the City Hall
Some accounts of Wilde's lecture tour cite this reference, or its more recent alternative name 'Old City Hall,' the assumption being Lincoln's first City Hall, a building extant at 920 O Street.
This was a 'city hall' in the usual sense of a municipal building. Completed 1879 as a Post Office and Courthouse, it later served as the seat of the Lincoln city government for 62 years.
However, on his American tour Wilde typically did not lecture in municipal office buildings, and, besides, City Hall did not house an auditorium.
2) the opera house
This reference would indicate that Wilde's lecture did, in fact, take place in a theater setting. But the lower case suggests it would not have been the main Opera House (formerly Hallo's and later Funke Opera House).
This is borne out by the listing (below) which not only indicates that the Opera House was otherwise engaged on April 24, it also confirms that Wilde lectured at a venue called City Hall.
But this listing also adds that the proprietor was a Fred Schmidt, and this piece of evidence helps to resolve the apparent conflict.
New York Dramatic Mirror, 1882
The City Hall Theatre
Confusion has arisen because Wilde's lecture took place at a theater that was known briefly as "City Hall," with the name used in the sense of a music or concert hall, as in his previous two lectures at Liberty Hall (Lawrence) and Corinthian Hall (Atchison) .
Frederick (Fred) Schmidt, a dry goods merchant, was an early developer in Lincoln, and the longtime owner of premises built c. 1878 that provided for commercial use on the ground floor, with a two-story height theater on the upper floor. It was here that Wilde lectured.
The words CITY HALL on the ornament
of the north facing cornice
By 1880, the city directory noted that the building stood on O Street opposite the government post office under the proprietorship of Schmidt and Jones., housing "City Hall, with a seating capacity of 1,000 used for all sorts of public purposes." These activities included dances of The Pleasant Hour Club, and, later, productions of The People's Theatre.
The building subsequently extended its commercial activities to both floors, occupants including Schmidt Dry Goods, The Union Pacific Tea Company, Grand Leader Department Store, Simon Galter's Men's Furnishings, and the Golden Eagle Department Store.
The inevitable modifications to the facade that made the structure unrecognizable, also masked its original use for more than a century.
Fortunately, the building's identity was reestablished in 2010 by Ed Zimmer, Historic Preservation Planner at the Lincoln/Lancaster County Planning Dept., following a fire that destroyed the building. His work in examining the revealed structure, and researching its heritage, is largely instrumental in enabling the former City Hall theater to be identified.
Lincoln, Nebraska interactive map
Journal Star (Lincoln, NE) - Report of Fire
Lincoln and the Adult Novelty Store