For the most part, Boston's history is best viewed when looking around or up. But sometimes, it pays to look down: Places such as downtown, the North End and Chinatown are filled with remnants of our commercial past, in the form of manhole covers.
A common sight around Boston are Bell System manhole covers, from back in the day when there was one national phone company that connected all of its regional subsidiaries (all, of course, stemming from the work of Alexander Graham Bell on Court Street).
But on Essex Street in Chinatown, next to the Verizon switching station that dates back to Ma Bell days, you'll find a couple of manhole covers proclaiming the existence of the New England Telephone and Telegraph Co., which dates back to the late 1800s (see this 1889 directory - 9M PDF).
On Washington Street, also in Chinatown, you'll find a cover reading "BLTWA." Alas, no BLTs with apples are stored beneath. The Boston Light Tension Wire Association ran wires under downtown streets to connect stockbroker ticker-tape machines.
In 1908, the Massachusetts Highway Commission, which regulated telephone and telegraph companies (naturally) in the state, ruled the association was not subject to state oversight because it did not conduct the "intelligence by electricity" the legislature had decided to regulate - it had no switchboard or any other equipment, it just provided private connections between stockbrokers (you can see the finding on page 145 of this report - 13M PDF).
Remember when utility companies had names that told you what they do? The granddaddy of today's Eversource was the Edison Electric Illuminating Co., established in 1886. In 1924, the company started its own radio station (see if you can figure out the call sign before clicking on the link).
The old Salem Street power plant in the North End also still bears the original company name.
Before National Grid (before even Keyspan and Boston Gas), Bostonians got their natural-gas service from Boston Consolidated Gas, which got its start in 1905 when the New England Gas and Coke Co. of Everett acquired a series of gas companies in the Boston area and consolidated them all into a single entity (among the companies it acquired was the Boston Gas Light Co., founded in 1822, originally to supply gas for lighting). In 1955, the company changed its name to Boston Gas.
Before the MWRA and the BWSC, we had the Boston Water Works.
Not all the manhole covers for companies that no longer exist are that old. Downtown is full of covers over fiber-optic lines run by companies started up just before and after the breakup of AT&T, including MCI, MFS McCourt and Level 3.