The title of the poem reveals the subject. The poet is critiquing the upheaval that the line gang's installation of telegraph and telegram lines is bringing to his once quiet and undisturbed rural setting. The poem is about how he resents the intrusion of the line gang.

He refers to line gang as "pioneering," alluding to the settlers who once arrived at unspoiled, natural places and disrupted them. He implies the line gang is careless, not so much cutting down trees as breaking them to make way for the "dead trees" (telephone and telegraph pools) the gang erects in their place.

He says the line gang is noisy as it works, in contrast to the "hush" or silence which will prevail when the lines later bring words via phone or telegram to people. The line gang "shouts" and "laugh[s]." In general, it is a nuisance, disturbing the narrator's peace.

In "The Line Gang" Robert Frost describes a team of men who are setting telephone and telegraph wires.

They begin by cutting down a forest, "replanting" the logs as telephone poles, and then stringing wires between the poles:

They throw a forest down less cut than broken.
They plant dead trees for living, and the dead
They string together with a living thread.

The wires will carry words, either spoken on a telephone or "beaten out" on a telegraph; as the words travel along the wire, however, they will be "as hushed as when they were a thought."  The men, though, do not work quietly: "they go past /
With shouts afar."

Frost was born in 1874 and died in 1963; he witnessed the rapid transformation of America from a mostly rural country to a mostly urban superpower.  In his personal life, he experienced urban life in his hometown of San Francisco and rural life in his adopted home of New England.

In "The Line Gang," Frost seems to be considering the progress of industrialization and urbanization.  His attitude toward this process is not simplistically "for" or "against."  He observes that the forest has been left "broken" by the chopping down of trees, but he also seems to admire the power and potential of the telephone and telegraph that can "set the wild at naught."

Critics have observed that Frost often expresses a "double" vision in his poems.  This can be seem in "The Line Gang."