Patrick Quirk Caples was born in Bilboa, County Limerick, Ireland, probably in 1829 or 1830, the son of Julia Quirk and her husband, Patrick Caples, a doctor. Nothing is known of his early family life. He travelled to Australia, probably in the 1850s, and had some success in the goldrushes there. In 1861 he joined the goldrush to Otago, New Zealand.
In 1862 Patrick Caples was elected to the Mining Board of Gabriel's District and as their representative went prospecting for gold, mainly from the head of Lake Wakatipu. He also became one of a number of explorers seeking a route from the Lake District to harbours on the West Coast, to improve transport to the goldfields. Of the many miners who went into the hills prospecting for gold, Caples was to be one of the few whose work was recorded.
In January 1863 he journeyed alone from the Dart settlement at the head of Lake Wakatipu up the Route Burn, cutting steps in the snow and ice to reach Harris Saddle. He was the first European to reach the river below, which he named the Hollyford. He followed the river down as far as Hidden Falls Creek, which he ascended to cross a saddle into the north branch of the Route Burn, explored by Charles Cameron and others not long before.
With fresh stores Caples returned to climb a peak above Harris Saddle. He observed a large lake to the west, with smoke lifting beyond, but lacked sufficient food to reach it. Instead, he went up the Hollyford into the saddle separating it from the Greenstone River, passed Lakes Howden and McKellar, then crossed to what is now called the Caples River, which he followed down to Lake Wakatipu.
There he met the surveyor James McKerrow, who gave him tracings of the most recent map of Otago, which included the West Coast from Milford Sound to Jackson Bay. McKerrow was unable to accompany Caples, who set off alone. Walking via the Greenstone he followed the Hollyford and reached Martin Bay on 9 March. Near the beach he observed a rough hut, and, afraid of hostile Maori, he camped without lighting a fire. After secretly examining the bay he returned up the Hollyford. Ravenously hungry from lack of food, he caught and ate several rats. For some reason he did not return to Lake Wakatipu by a previously used route, but made an astonishing journey across country to Nokomai.
Caples found only traces of gold on these journeys, but he recorded his observations in his report to Vincent Pyke, secretary of the Gold Fields Department, and drew up a very accurate map of the area. Caples did not receive the recognition he might have for his discoveries, mainly because James Hector also explored the Hollyford–Greenstone–Wakatipu route a few months later, and the publicity he received obscured previous efforts by Caples and others. The chief surveyor of Otago, J. T. Thomson, was, however, aware of Caples's work. He subsequently incorporated some of the geographical features Caples had noted and named, including the Hollyford Valley, into a map of north-west Otago. The accuracy of Caples's work facilitated the progress of other surveyors who eventually followed in his path.
In 1864 Caples and five miners crossed the Rees Saddle into the Dart River to search for reported gold, but little was found and after days of snow they retreated to the Rees. Caples was the first to refer to the Dart Glacier, which they saw on this trip.
By the early 1870s Caples had settled in Reefton. Although he did not prospect in the area, he discovered reefs at Point Reefton, Moonlight and Georgetown. In December 1873 Georgetown, 11 miles east of Reefton, was renamed Caplestown in his honour. Caples is said to have erected the first quartz-crushing battery on the West Coast.
In 1873 Patrick Caples was elected to the local district board. In 1877 he was elected for the Boatman's riding, Inangahua county. From November 1878 until November 1879 he was chairman of the Inangahua County Council. He also became a manager of many of the quartz mines in the district. Although he lived quietly, he always maintained a community profile of the highest integrity. He never sought financial reimbursement for his maps or discoveries.
Patrick Caples did not marry. He died at Reefton on 27 November 1904, aged 74, and was buried in the Burkes Creek cemetery. Part of his home was later incorporated into a motel complex on the corner of Sinnamon Street and Broadway in Reefton.