Oh, it's mainly because Massachusetts bought Maine from a guy. Seem odd to you? It sure does to me, so let's see why and how that happened.

Lets breeze through some relavent background first... The English became very interested in North America starting in the 1560s and mainly for two reasons, locating the Northwest Passage and all that stolen Spanish gold literally floating around. Both of these ideas started to build interest in establishing a colony and in 1578 the first English patent to colonize land north of occupied Spanish Florida was issued by Queen Elizabeth I to a man named Humphrey Gilbert. After colonizing Ireland, Gilbert had written one of the first works advocating an English settlement across the Atlantic and his reasoning for creating one was to secure the passage (and trade wealth it would provide) exclusively for England and to have a base from which privateering raids by the Queen's famed Sea Dogs - privateers (pirates) like Francis Drake, John Hawkins, Martin Frobisher, and Walter Raleigh - could be launched on Spanish treasure ships. He also believed America to be the same island as Atlantis, Plato's long lost continent, which increased his confidence in the existence of the Northwest Passage just north of the island that would lead to Cataia (China). He was totally wrong about all of that. By the mid 1580s we start to see a change in mentality of those funding these expeditions and visions of naval base colonies.

Martin Frobisher spent five years convincing investors from trade investment firms to fund his voyage and in 1576 he finally sailed west in an attempt to find the passage, largely motivated by the writtings of Gilbert from the late 1560s and early 1570s, and Gilbert also invested financially in the Frobisher expeditions. The trade revenue from the passage was the proposed motivation for these groups, who were private companies that invested primarily in trade voyages as financial sponsors who would get a cut of the profit in return. He came back with pyrite, or fool's gold, and that funded a 1577 return trip and another in 1578, all returning massive amounts of rocks that would later be properly identified as almost worthless. Then comes the patent and Gilbert's two voyages, the second of which takes his life in 1583. Walter Raleigh, Gilbert's half-brother, gets the patent's southern half covering land south of Newfoundland to "occupied Spanish Florida", or (as the English saw it) to modern day South Carolina, in 1584. That same year Richard Hakluyt published a continuation of Gilbert's colonization idea, however this time the focus heavily changed to being on the resources a colony itself could provide. That idea spread and soon investment groups and wealthy men were ready to invest in colonies.

By the early 1600s folks like Raleigh Gilbert, who was Humphrey's son, and George Popham were ready to be the men who established a colony in English America, being the land claimed in 1584 by Walter Raleigh between Spanish Florida and New France. Behind them were even more important, and well off, financiers willing to commit. Ferdinando Gorges, who was the military governor of Plymouth, John Gilbert, son of Humphrey and Raliegh Gilbert's older brother, and Lord Cheif Justice of England, John Popham, who was also uncle to George Popham, are the most vested and notable of the investors of this joint-stock venture. In 1603 Elizabeth I died and the throne passed to James I who was accepting of the proposal for private funding to send private citizens to settle colonies that would provide a financial return, a cut of which would go to the King just for his permission to use his lands. In 1604 the Treaty of London establishes peace between England and Spain.

Others with more fame today, like Hakluyt, John Smith, Christopher Newport, etc., would invest in the Virginia Company of London, granted a charter to colonize southern Virginia. This company would go on to found Jamestown in 1607. The sister company was the Virginia Company of Plymouth and that's the one our investors funded. They were granted a charter for northern Virginia, as specified by longitudinal lines, and would also establish a colony in 1607 and in modern day Maine. George Popham would become the leader of the colony with Raleigh Gilbert being second in command. Lord Popham was the president of the whole operation, but he died in 1607 only weeks after the colonists left England and John Gilbert then became president. The colonists experienced colder weather than they hoped for and struggled to establish themselves, then in 1608 George Popham died. Shortly after a ship arrived with the news that John Gilbert had also died, and that provided an unexpected inheritance to Raleigh Gilbert. With members of leadership dead both in the colony and in England and coupled with the difficulty of the settlement, the colony was abandoned and Gilbert returned to England in order to claim his inheritance... He was only 23 when they left England for North America and this inheritance would provide for the rest of his life. Ferdinando Gorges remained engaged and became president of Plymouth Company, but the venture was effectively dead. In 1620 his next effort was authorized by James and he became proprietor of northern Virginia. Eyes focused further south on expanding the holding made in Jamestown which had its own troubles, then came a group of religious seperatists we call the Pilgrims seeking funding to build their own colony, and the Merchant Adventures were convinced the idea was solid after making some demands about the colonists and repayment details.

The Pilgrims sailed in late 1620, arriving in Nov of that year some 200 miles north of their target, the Hudson River, located in southern Virginia and under authority of the London Company. They instead landed in northern Virginia, under control of the new Gorges endeavor (The Council of New England), from whom they had not recieced permission to do so. Enter negotiations with John Pierce of the London company and Gorges to permit the settlement to exist, and he ultimately made it happen in the Pierce Grant. The Council issues more grants, including one to Gorges and John Mason covering lands in modern New Hampshire and Maine. Then the King died and war came back. Gorges would become occupied as military governor and would be unable to focus on colonies in what he officially named Maine or on the Council.

The Pierce Grant ultimately allowing the Pilgrims to stay would become his own undoing. Some other folks had made investments that pretty much flopped in the 1620s, and those ultimately became morphed into a new venture known as Massachusetts Bay Colony, which was largely puritans who had been inspired by the seemingly stable society in Plymouth Plantation run by the Pilgrims nearby. They recieved a royal charter for their endeavor and were permitted within land under authority of the Council. Mason also split his holding with Gorges, creating New Hampshire. In 1630 Gorges resigned as military governor and again focused on Maine, where he had helped create some small fishing communities over the previous decade but nothing of any real note.

Gorges realized the exploding population of Massachusetts Bay Colony and subsequent growth in authority would undo the Council of New England, so he dissolved it and sought a new charter as Governor of New England, retaining his holding of his remaining portion of Maine. He planned to sail to America and govern the region but the trip never happened and eventually Gorges died, in 1647, having never achieved his vision. Meanwhile Massachusetts Bay Colony had continued to grow in size and power, had survived the Pequot War and had removed many Natives by selling them in the Caribbean. The power continued to shift and by the late 1670s the power of Massachusetts Bay was revealed in King Phillip's War, an extremely violent purging of the local Natives, their King, and his family in which both sides suffered massive loses. Despite efforts by both the son and grandson of Gorges no major colony ever existed in Maine. In 1677 Ferdinando Gorges' grandson, also named Ferdinando, sold his family's rights over Maine to Massachusetts Bay Colony for 1,250£, ending decades of legal battles over validity of the land grants by seperate kings decades prior.