Lines like this were built during the prosperous 1890s or so when the telegraph was gaining a LOT of popularity. These circuits replaced simpler threaded lines (superceding threadless routes) and sometimes retained the same iron wire. Such c.1890s pole line construction as seen pretty much was standard with Western Union until the early teens when total rebuilds throughout much of their territory (at least here in New England) involved using new (cedar) poles with hard-drawn copper wire (replacing the former iron wire) strung upon new 10-pin crossarms. Pretty much the only stuff that was re-used from the 1890s construction were the double-petticoat insulators (CD 145s), insulator pins, braces and other reusable hardware. Lots of this remained in service through the 1970s and still can be found in the wild...either on the ground (most likely) or still in the air (in very few instances).

Precarious poles (aka potentially rotting-at-the-base ones) were sometimes braced for support as seen here!