Available documents have shown that William C Bell was a photographer from 1894 through 1944 when he died at age 75. While his base operation seemed to be in York, PA, (he also kept a residence there) he had as many as four other studios operating at the same time in neighboring towns. Piecing it together through city directories of these towns met missing pages and missing years but this is the best timeline result that could be made.
York city directories after 1904, are available in odd years only
1894 through 1902
York, PA, studio at 6 w Market
1904 through 1913
York, PA, studio at 10-12 w Market
1915 through 1921
York, PA, apparently either works out of his home at 302 e King or works in one of the other studios in other towns
1923 through 1925
York, PA, studio at 21 s George
York, PA, studio at 25 s George
1931 through 1933
York, PA, studio at 133 s George
York, PA, studio at 38 e Market
1935 to 1944
York studio location is unknown
1906 Dec 01 The Wilkes-Barre, PA, Record, news item mentions Bell has returned from York, so possibly he had a gallery there at that time.
1914 - 1919 Wilkes-Barre, PA city directory as photographer at 39 s Main
1921 Wilkes-Barre, PA, NOT in city directory
1886, 1888, 1904, 1908, 1909, 1910, 1912, 1923, 1928, 1930, 1932 NOT in West Chester, PA, available directories
The studio in Westchester, PA, at Market and High streets, either occurred before 1886 or only for a short period during the missing years such as 1911 and 1924.
There was also a studio at Frederick, MD, as mentioned in an 1891 newspaper item. City directories from Frederick, MD, are available from 1925 or later so this could not be confirmed. (See article in next row)
This cabinet card from West Chester, MD, can only be dated at around 1891.
Pittston Gazette - 19 Nov 1912
The (York, PA) Gazette and Daily - 11 Mar 1927
Example from PhotoTree
Finished around 1891
photographer: W C Bell
6 West Market St, York, PA
From the Flickr Collection of Ken