From the Preface: One of the most unheralded landmarks in Greater New York is the Brooklyn Broadway/Jamaica Avenue Elevated Railroad (today known as the J/Z line). Built in stages between 1885 and 1918 it has been a vital transportation route for nearly one hundred and forty years. When the first three segments of the line opened in 1885, 1888, and 1893, Brooklyn was still an independent city with a population 806,000 which made it the fourth largest city in the United States. Originally an extension of Brooklyn’s first El, the Lexington Avenue line which opened on May 13th 1885 from York & Washington Streets to Gates Avenue on Broadway via York Street, Hudson Street, Park Avenue, Grand Avenue, and Lexington Avenue before east onto Broadway for three blocks. From there it was extended eastward before reaching Van Siclen Avenue on December 3rd 1885. In 1888 the Broadway portion of the line was extended west to first Driggs Avenue on June 25th 1888 in Williamsburg, and finally to Broadway Ferry the following month on July 14th 1888. The book that follows, The Evolution of an El: A Structural Timeline of the Construction of the Brooklyn Broadway/Jamaica Avenue Elevated Railroad from 1885-1918 in Contemporary Photographs documents, in pictures taken by the Author between 1977 and 2023. Some of the pictures included will be of less than picture perfect quality due to the old Kodak 100 & 110 Instamatic cameras used in the earliest shots, the disposable 35mm cameras used in later ones. Some of these early pictures taken by the Author show some fading due to age, and in a few cases water damage, the latter pictures still being included because they contain images of those parts of the EL that are long gone. The newest pictures taken in April 2023 contain some the clearest images due to the superior quality of the camera used. The earlier shots are included to highlight the changes made to the Els structure and stations in the forty-five years between the oldest pictures dating back to 1978 and the latest ones taken in 2023. The chapters/pictures do not cover the line from point to point but rather the years in which each segment was built, the emphasis being on the design of the structure erected in a given year. For instance, as will be repeated later in the book, while the opening year of that portion of the EL between Broadway Junction and Alabama Avenue is listed as 1885, the fact of the matter is the original structure was replaced in its entirety by a completely new structure erected during the 1915-16 reconstruction, reinforcement, and third tracking of the EL between Marcy Avenue and Broadway Junction. Done in the midst of the massive expansion of Greater New York’s elevated and subway network between 1913 and 1920 (otherwise known as the Dual Contracts), the El structure design of the reconstruction years, 1915 & 1916, is the standardized design employed in the Dual Contract period. So even though the El in this section had by this time been operating for thirty years, this part is not in the chapter covering 1885 since no part of the original 1885 structure exists.