In the early twentieth century numbers began to fall, both because many were taken for use in the First World War, and because of the increasing mechanisation of agriculture.

[6] In the late seventeenth century, stallions of Friesian and Flemish stock from the Low Countries were imported to Scotland and bred to local mares.

Written pedigrees were kept of these foals beginning in the early nineteenth century, and in 1806, a filly, later known as "Lampits mare" after the farm name of her owner, was born that traced her lineage to the black stallion.

[6] This programme consisted of local agriculture improvement societies holding breed shows to choose the best stallion, whose owner was then awarded a monetary prize.

The owner was then required, in return for additional monies, to take the stallion throughout a designated area, breeding to the local mares.

It was started by two breeders dedicated to improving the breed, who also were responsible in large part for the introduction of Shire blood into the Clydesdale.

[11]: 284–285 Large numbers of Clydesdales were exported from Scotland in the late nineteenth and early twentieth centuries, with 1617 stallions leaving the country in 1911 alone.

These horses were exported to other countries in the British Empire, as well as North and South America, continental Europe, and Russia.

[15] By the late 1960s, it was noted that "Excellent Clydesdale horses are bred in Victoria and New Zealand; but, at least in the former place, it is considered advisable to keep up the type by frequent importations from England.

[18] In 2010, the worldwide Clydesdale horse population was estimated to be 5,000,[19] with around 4,000 in the United States and Canada,[12] 800 in the UK,[7] and the rest in other countries, including Russia, Japan, Germany, and South Africa.[11]: 284–285 .

[21] According to The Livestock Conservancy, "The North American population of Clydesdale horses had increased steadily for several decades, but a sharp decline began around 2010, prompted by the economic downturn that affected the entire equine market.

Beginning in the 1940s, breeding animals were selected to produce taller horses that looked more impressive in parades and shows.

The breed has a straight facial profile or a slight Roman nose, broad forehead, and wide muzzle.

Buyers do not favour Sabino-like horses, despite one draught-breed writer theorising that they are needed to keep the desired coat colours and texture.

Clydesdales are known to be the popular breed choice with carriage services and parade horses because of their white, feathered legs.

However, those efforts were not seen as successful, as Irish Draught breeders thought the Clydesdale blood made their horses coarser and prone to lower leg faults, such as tied-in below the knee.

[11]: 374–375 The Australian Draught horse was created using European draft breeds, including the Clydesdale, imported in the late 1800s.

[30] In the early 1900s it was considered profitable to breed Clydesdale stallions to Dales Pony mares to create a mid-sized draught horses for pulling commercial wagons and military artillery.

[12]: 294 [11]: 173 The Clydesdale contributed to the development of the Gypsy horse in Great Britain along with Friesian, Shire and Dale, although no written records were kept.