Alright here it is (it was to begin in Boston):
The year is 1997. The combustion engine was never invented. Heavier-than-air flight was never invented. Long distance travel is on trains, steam-powered airships, or steam ships. Electricity exists, but is limited to simple circuits and things like light bulbs (no electric motors). For most people, intra-city travel is via trolleys, steam buses, or cycles (though horses are more common in the more rural areas). Only the rich can afford personal steam carriages. Both still and motion pictures exist, though not of the quality we enjoy today (and also entirely analog). Computers exist, but they are very large and entirely mechanical. Rockets have been invented, and space travel is the new frontier.
Boston specifics:
Rapid transit:
Boston’s rapid transit system, known and the T, uses a flywheel energy system to power its trains. The flywheels are spun to very high speeds and its momentum allows energy to be extracted from it to generate forward movement. While trains are stopped at stations, externally produced steam is used to add energy back into the system. This type of system allows trains to operate in underground tunnels where conventional steam locomotives would generate too much exhaust. The modern T system contains both elevated and underground segments.
Steamworks:
During the early 1800s, large factories increasingly had their own steam engines to power their factories, but most smaller homes or businesses could not afford them. Thus, by the 1850s, cities started to construct large facilities to generate steam to be piped out for mechanical and heating use in smaller locations. When it was built in 1875, Boston Public Steamworks was the largest in the world. Now, it’s the oldest system with its original hardware still running, with other cities opting to modernize or upgrade their systems. Most larger or more affluent structures have on-site generation, so the system is currently chiefly used by the poorer sections of the city. Because of its age, the system can be prone to breaking down.
Steam Buses:
While most cities developed interurban networks in the early 1900s, Boston’s construction of its subway system and its tight, haphazard streets meant that trams never gained a foothold. Instead, to fill the gaps in service, it turned to the construction of free-roaming steam buses.
Roads:
Roads are used by buses, cyclists, and pedestrians to move about the city. Personal steam carriages are also used, though only by the more affluent citizens. Horses, though common in rural areas, are not permitted in the city for sanitary and safety reasons. Freight traveling locally can be carried by steam trucks, cycles, or by foot, depending on what it is.
Rail network:
Boston’s rail network consists of both local commuter trains and long-distance intercity trains. Locomotives are powered by steam engines. There is also a freight network connecting to the Port of Boston. This is how most of the freight travels to and from places away from the coast.
Air travel:
East of Boston, on some land reclaimed from the sea, there is the Boston International Aerodrome. Airships land and depart from here. There is some cargo that travels via airship as well. Airships can travel to any place regardless of terrain. The advantage of airships is that they can travel directly to their destination regardless of the terrain. They are the fastest form of travel, but their limited space on board means that it’s also the most expensive. Mail is the only form of cargo in which airships dominate.
Sea Travel:
The Port of Boston is a major seaport on the east coast of the United States. Most of the offshore freight travels to and from Boston this way. The part of the port closest to downtown is where all the passenger traffic docks. These include everything from local ferries to the islands in Boston Harbor to large ocean liners to places across the globe. Sea travel is the slowest form of transport, but their ability to handle huge loads at once means that it is much cheaper than air travel.
Long distance communication:
The two forms of long distance communication are mail and telegraph. Mail can travel locally by foot, cycle, or steam truck. For longer distances, it travels mostly via airship, though some portions still travel by trains and ships. Ships in particular are much cheaper if one is willing to sacrifice speed. Telegrams are much faster than mail, but the nature of how they are sent means that the cost goes up as the message gets longer. Telegraphs for the general public are found in post offices and banks. Some large businesses also have their own. Private telegraphs for residences are rare because of their high expense.
With some inspirational videos: