Question: What year did the company, who operated Slick Mine No. 91 after 1923, begin operations?

Context paragraphs:
Raho City Taxi: Raho City Taxi is a taxi company based in Hargeisa, the capital of the northwestern Somaliland region of Somalia.  Established in 2012, it is one of a several new cab firms to begin operations in the region.  As of 2012, Raho City Taxi has a fleet of around 40 vehicles, which include small sedans and vans capable of accommodating up to seven passengers at a time.  Each taxicab is distinguished by its yellow exterior design and numeric labels.

Bethlehem Steel: The Bethlehem Steel Corporation (commonly called Bethlehem Steel) was a steel and shipbuilding company that began operations in 1904 and was America's second-largest steel producer and largest shipbuilder.

Bonn–Oberkassel train ferry: The Bonn–Oberkassel train ferry was a German train ferry operated by the Rhenish Railway Company from 1870 to connect its right and left Rhine railways.  It was the last of six train ferries to begin operations across the Rhine in Germany and the second to last to close.

Tocoma Dam: The Manuel Piar Hydroelectric Power Plant (Tocoma Dam) is under construction and it is the last hydroelectric development project in the Lower Caroní River Basin of Venezuela.  The project includes the installation of 2320 MW MW to generate an annual average energy of 12,100 GWh .  Ten Kaplan generator units, of 230 MW , manufactured by Argentinian company IMPSA, were predicted to begin operations between 2012 and 2014.  The first generator was installed but not yet commissioned in April 2012.  Behind scheduled, the dam began to impound its reservoir on 16 November 2015.  These units had the world record as of 2012 in power generation at nominal head for Kaplan turbines.  The diameter of the runner is 8.6 m and nominal head is 34.65 m with claimed output up to 232 MW .

Slickville Historic District: Slickville Historic District is a national historic district located at Salem Township, Westmoreland County, Pennsylvania.  It encompasses 90 contributing buildings and 1 contributing structure in the unincorporated village of Slickville.  The company built mining town was built between 1916 and 1923.  The contributing resources include workers and managers housing, four utilitarian mine-related buildings, a church, a school, a pump house, and a company store.  The community was originally developed by the Cambria Steel Company, and later acquired by Bethlehem Steel who operated Slick Mine No. 91 after 1923.

Spring Airlines Japan: Spring Airlines Japan Co., Ltd. (春秋航空日本株式会社 , Shunjū Kōkū Nihon Kabushiki Gaisha ) is a low-cost airline headquartered in Kozunomori, Narita, Japan.  It is 33% owned by Spring Airlines, a Chinese low-cost carrier, with the remainder held by various Japanese investors.  The airline began operations in August 2014, having originally planned to begin operations in autumn 2013.

Apsara International Air: Apsara International Air (Khmer: អាកាសចរណ៍ អប្សរា អ៊ែរ ) is an airline that currently operates between Phnom Penh and Siem Reap.  The airline had its inaugural flight in October 2014 and plans to begin operations between Siem Reap and Sihanoukville by the end of the year.

Smokers Express: Smokers Express (or Smokers Express Airlines) was a Cocoa Beach, Florida-based company that would have provided smoking flights to destinations within the United States.  Founded in 1993 by William Walts and George "Mickey" Richardson, the company never received enough funding to begin operations.

Waves (Airline): Waves is a technology-driven airline based in Guernsey in the Channel Islands.  The airline is a subsidiary of Waves Technologies Limited, which is a privately owned company.  It plans to operate from its hub at Guernsey Airport to up to 15 regional airports in and around the Channel Islands.  Waves also plans to undertake cargo and medevac activities, on demand.  It is scheduled to begin operations in July 2017.

Televisa (Venezuela): Televisa (not related with the Mexican television network, Televisa), officially known as the Televisión Independiente, S.A. became the first privately owned television station to begin operations in Venezuela.  It was the second television station to begin operations after the state-owned Televisora Nacional.  In 1960, Televisa was purchased by and re-branded as Venevisión and became in business' Cisneros family.

Supporting paragraphs: Slickville Historic District Bethlehem Steel
Answer: 1904