The race began with a neutralised start at the Market Place at about 10:30 BST, where riders travelled through the opening section at a controlled speed before the official racing got under way on Boston Road.
The town hosted a day-long festival of cycling and family entertainment, and also screened live race coverage in the Market Place.
Dale Broughton, leader of Boston Borough Council, said it was a landmark day for the town and for East Lindsey.
“We always do things big in Boston. Hosting the start of the stage… racing through the Wolds and finishing on Skegness seafront will be a day that residents, visitors and businesses will remember.”
Cycling enthusiasts Jo Hartley and Pat O’Connell travelled from York to watch the beginning of the race, and were also hoping to catch a glimpse of the end.
Jo said: “I like to pick somewhere I’ve not been before. So I look at the race and go, ‘I don’t know that town, lets go and visit it’. I wanted to know what Boston was like, so I chose here.”
Stood among the spectators was former Tour de France winner Geraint Thomas.
“Yesterday was really good. It was super exciting to watch,” he said. “So yes, we will see what today brings.”