Lochwinnoch lies a mile north-west of the main A737 road some eight miles south-west of Paisley. It owes its growth to the River Calder, which flows from the high ground to the north-west into what was originally known as Loch Winnoch. The loch has since been renamed Castle Semple, after the Castle built by the Semple family at its east end in the 1400s. Neither the castle nor the grand house that replaced it now stand, though the nearby Collegiate Church is remarkably well preserved.
The name probably originates as the Loch of St Winnan, a Saint who seems to have passed this way in the 500s and whose name is also attached to Kilwinning, or Church of St Winnan, rather nearer the coast. The name Winnan seems to be an early form of Finian.
Lochwinnoch itself first grew up around a church established here by the monks of Paisley Abbey in the 1200s. It was still primarily an agricultural village when a new church was built, perhaps on the site of the old, in 1729. This church too has passed out of use, but its west gable end and clock remain standing on rising ground at the north-east end of today's village. This is now known as Auld Simon and when the rest of the church was demolished it was preserved at the insistence of local weavers.
Lochwinnoch started to move away from its agricultural roots in 1722, when the first thread mill was built on the banks of the River Calder. A linen bleachworks followed, as did more thread mills, cotton mills and a limeworks. Then coal pits were dug locally to provide coal so that steam power could supplement the water power from the river for the mills.
By 1799 Lochwinnoch had grown into a settlement of more than 500 people. Many lived in the planned extension to Lochwinnoch, to the west of the existing town, built by the laird, William MacDowall, in the 1790s. This included two new churches, whose construction rendered Auld Simon redundant.
The MacDowell family had purchased the Semple estate in 1727. And it was same William MacDowell who demolished the original Castle Semple to make room for (and provide building materials for) the Castle Semple House he built in its place in 1735 overlooking the east end of the loch. This burned down in 1935 and its shell was demolished in the 1960s.
The railway passed up the far side of Castle Semple Loch in 1840, leaving Lochwinnoch Station three quarters of a mile from the centre of Lochwinnoch. A loop that opened in 1905 passed through Lochwinnoch itself, but this had closed by 1966, by which time the textile industry had also all but disappeared from the town.
Today's Lochwinnoch is a town that continues to grow, being within easy commuting distance of Glasgow. Despite this the centre retains a sense of identity, and elements like Auld Simon add considerable charm.
Today the town also serves as an important centre for watersports. The Castle Semple Country Park, on the south edge of the town, is home many rowing regattas and other events held on Castle Semple Loch.