Milton (aka Middletune [Mid-le-tun-e] or the middle town) was historically far more important than Sittingbourne. The Isles of Sheppey and Elmley fell within its manor (though Harty belonged to Faversham). Milton boasted a Portreve which meant that international trade could be carried out. The "Regis" of course means "King's", in other words the manor of Milton was a royal manor, the steward reporting directly to the King, not to a local Lord. In Elizabethan times Sittingbourne was knwon chiefly for its inns along the Watling Street. Gentlemen travelling along the Watling Street would lodge their servants in Sittingbourne, but themselves adjourne to Milton where the lodgings were of better quality.
The came the railway. Milton is on a hilltop, surrounded historically by marshes, not ideal for railway building. There was also local opposition to the building of the line. the line therefore followed the route of Watling Street, and hence the station and goods yard were at Sittingbourne. Industry grew up around the railway, and housing around the industry. Milton went into gentile decline, aided by the siltting up of the creek by effluent from the paper mills.