As the two maps show, the residence of William J. Montgomery did not appear in the 1889 map. It was constructed between 1889 and 1899 since it showed up in the 1899 map. The Directory shows that in 1900, the house still exist. In google street view, the residence nowadays is the same as the image from 1899.
In the 1910 United States Federal Census, there is a William J. Montgomery who lived on Greens Street. It is possible that he is the owner of the house because the house number 6124 on Greene Street faces the location of the residence. Montgomery was the president of City Material Bank and was at the age of 45 in 1910.
Google Street View
Boyd's Co-partnership and Residence Business Directory of Philadelphia City, 1900