An early Lincolnshire Railway Map
Although the extracts below are from a map that accompanied the March 1850 Bradshaw's Guide, it's clearly a few years earlier. The solid lines indicate completed railways, broken lines proposed routes and railways under construction.
This preceeds the opening of the "Towns Route" (the present East Coast Main Line). The Great Northern's Loop line through Boston and Lincoln was then part of the main East Coast route between London snd the North.
King's Cross had not been built yet, so passengers would reach Lincolnshire from either Fenchurch Street and travel via Ely and Peterborough, or from Euston Square (nowadays Euston Station), via Northampton and Peterborough.
The East Lincolnshire Line is extant, alouth the branches to Spilsby, Skegness, and Mablethorpe had yet to be constructed. It's main function at the time was to provide a direct route to Hull via the ferry at New Holland.
Lincoln was linked with Newark, Sheffield, and Grimsby. Scunthorpe and Grantham had yet to be connected to the rail network.
The map also gives us a fascinating glimpse at proposed routes. In this instance a branch from Grantham to Sleaford, and another (never built) between Grantham and Spalding via Folkingham, from where another branch woukd diverge to Boston.
There is a little early documentation of the route, shown below. As it transpired, the line to Sleaford was extended Eastwards to Boston and, what would later become the Midland & Great Northern, routed via Bourne. Folkingham would never have its own station or become a junction, as once intended. No doubt this was to avoid the expense required by engineering on the route, so the railways chosen route used flatter terrain.