Twain makes it clear that his ambition to work on a steamboat was not unique to him: it was something that every boy wanted to be. It is important to recognise that this youthful ambition was a direct result of the context that Twain grew up in. For him, growing up on the banks of the Mississippi, the river was an important life-line in terms of trade and news, and therefore steamboats were respected and revered and eagerly awaited. Note how all the people react to the coming of the steamboat in this quote:
The town drunkard stirs, the clerks wake up, a furious clatter of drays follows, every house and store pours out a human contribution, and all in a twinkling the dead town is alive and moving. Drays, carts, men, boys, all go hurrying from many quarters to a common center, the wharf. Assembled there, the people fasten their eyes upon the coming boat as upon a wonder they are seeing for the first time.
Twain goes on to describe when the steamboat actually arrives and the intense flurry of activity as freight is taken off and put on and then how everybody goes back to their homes after the steamboat leaves and life continues as normal. It is not hard to understand therefore the ambition of many boys such as Twain to work on a steamboat and be greeted in this way by every village they came across.
A modern day equivalent would therefore have to be something contextual to the setting, as clearly a boy of Twain's generation who grew up away from a river would not want to work on a steamship. It would have to be a career that appeared to be glamorous because of all the travelling involved and the way that people greeted that person. Perhaps a good modern day equivalent would be a pilot who delivers aid to various groups of people in the developing world. This would be a similarly glamorous job and would also guarantee an appreciative audience.