Overhead pole lines with dozens of ten-pin crossarms upon them with incredible mazes of wires was considered "blight" by big-city residents and New York City was no exception. Here we see a telegraph construction crew feeding paired cable in an underground conduit along 6th Street. The telephone companies quickly followed suit and "buried" their multi-paired enclosed cables within NYC (and other larger US city streets) by 1890...if not earlier. By 1900 a lot of those big open-wire lines that were strung along major city streets in the United States were relocated underground. So...where did all of the insulators go? Back in those days it wasn't a throw-away society and most likely many of the insulators dismantled from the big poles were either put into service elsewhere or sold on the auction market. That is...those in good condition and of "standard" styles. Keep in mind that this material was only in service for a couple decades or less.

It is also interesting to note that the basic method of reeling twisted-pair conduit as seen above into underground conduit has not changed much in the past 120 years or so. The same holds true for cable-TV, telephone fiber and electric distribution cables of all sizes that presently network beneath city streets.