Was the influx of labor into the North accompanied by rapid technological innovation, infrastructure development, and urbanization?

If you are referring to the period of reconstruction after the Civil War, then the answer would be yes. At this time, much of the North was not only structurally stable, but economically as well due to the fact that the North had more industrial areas with which to produce goods faster, plus did not have to pay the reparations that the South did after the war. Much of the areas in the North were converted into war time factories which were able to produce things like guns and ammunition quicker than the South during the Civil War, and was just as easy to convert back to civil factories which would produce the steel needed to rebuild what was lost during the war. Along with the fact of many more opportunities were offered in the North at this time with there being an influx of work for both the urban and rural areas which meant that one could work in a factory, be a farmer, or whatever they chose to be, versus in the South where much of the work was mainly rural and only were able to offer jobs such as farming and ranching.