In J. W. Pepper's 1897 catalogue we are provided with a brief sketch of the company's early history in the city of Philadelphia.
Here's what it says in the upper left-hand corner of the page above:
J. W. Pepper commenced business, in a small way, in 1876 (Centennial Year) at 9th and Filbert Streets [832 Filbert Street, to be exact], as a publisher of band, orchestra and miscellaneous music. In 1881 it became necessary, on account of the growth of the business, to secure larger quarters, and he removed to 8th and Locust Streets [234 S. 8th Street, to be exact], to a building 22.5 ft. by 100 ft., with four floors. At that time he added as a branch to the business, all kinds of musical instruments, giving particular attention to those used in bands and orchestras. He soon afterwards added a factory for the manufacture of band instruments, which has grown, during the last fourteen years, to the largest and most complete establishment of its character in the United States.Here's what that building looked like in 1883, which was twelve years before the first Sousaphone was built:
The account continues: "In order to secure needed space for the increasing business, it became necessary, at the beginning of 1890, to purchase an adjoining building, and this, together with the corner property, was torn down and the building illustrated on this page [at the top of this post], erected." Here's a better view of Pepper's new facility:
The account concludes: "As noted, this building contains, with basement (in which all of the heavy newspaper and lithograph presses are located) seven floors, each of which is 45 ft. by 100 ft., and is the most complete establishment of its character in the country."
It is in this building that the very first Sousaphone was built in 1895. We are even told of two of the men who were in high-level positions in Pepper's factory at that time, and may very well have worked on the Sousaphone: Alexander LeForrestier, who was the head of the Bell and Tube Making, and Construction Departments; and Walter Barnes, who managed the Valve Making Department.
Sadly, the building is long gone, but here's what you would have seen upon entering the front doors back in 1894 (images below are from Pepper's catalogue of that year):
And here are the spaces in which the first Sousaphone would have been created:
Shortly after this building had opened in 1890, Frank M. Stevens paid it a visit and reported back to The Music Trades. Here's what he shared, which was reprinted in an 1891 edition of Pepper's Musical Times and Band Journal: