The summer solstice has been marked by human beings for as long as there have been human beings — it is the single most astronomically obvious event in the solar year, the day when the sun rises furthest north, reaches its greatest height and sets furthest north. Megalithic structures across northern Europe are aligned to the midsummer sunrise: Stonehenge most famously, but also Newgrange (aligned to the winter solstice), the avenue at Avebury and dozens of lesser-known monuments. The solstice was being deliberately observed and celebrated at least five thousand years before the word "Litha" was coined.
The name "Litha" comes from the Old English liða — the name for the two midsummer months in the Anglo-Saxon calendar (before June and after June, roughly). It was adopted by the 20th-century modern pagan movement as the festival name for the summer solstice. Medieval Midsummer — celebrated across Europe from the 12th century onward on the eve of the Feast of St John the Baptist (24 June) — was one of the great popular festivals of the year: bonfires, processions, the gathering of magical herbs, the rolling of burning wheels downhill.
Midsummer fires were lit across Britain, Ireland, Scandinavia and central Europe — on hilltops, at crossroads, beside sacred springs. Their smoke was held to purify and protect; people and cattle leapt through them. The resemblance to Beltane is not coincidental: both are fire festivals at astronomical turning points, both involve the purification and protection of the community and its livestock, both are moments when the boundary between the human world and the Otherworld is unusually permeable.