Here I mett Capt. John Richards of Boston who was going home, So being very glad of his Company we Rode something harder than hitherto, and missing my way in going up a very steep Hill, my horse dropt down under me as Dead; this new surprize no little hurt me meeting it Just at the Entrance into Dedham from whence we intended to reach home that night. But was now obliged to gett another Hors there and leave my own, resolving for Boston that night if possible.

As Massachusetts teacher Sarah Kemble Knight presents it in her 1705 diary, the exhaustion of her never-named horse was something more than a mere inconvenience, but less than a tragedy. The surprise still "no little hurt me" despite her being in just about the best possible place to have to swap out horses. But she--and whichever Dedham stable owner she encountered--saw no drama in swapping out horses.

Some people absolutely did develop stronger bonds with their horse. Right around the time of Knight's journey, a horse owner from Appomac in Virginia named their mare "Noby." Contemporary journals from the same area indicate that naming an animal was a sign of affection, not just utility--f.ex. cases where only one cow is noted as having a name, and is described with extra tenderness.

But in general, Knight's matter-of-factness about the horses that enabled her Boston-New York trip reflects the evolution of advice prescribed in horse-training and related manuals. Karen Raber and Treva Tucker sum up the general arc in their introduction to The Culture of the Horse: Status, Discipline, and Identity in the Early Modern World.

In the 16th and early 17th century, different types of texts recommend force, even abuse, for training horses--the idea being very much a rational man versus irrational nature combat. "Bit-Books" are just that: descriptions and illustrations of bits, concentrating on how the human can gain forceful control over the horse. Pia Cunco describes the early modern attitude towards bits:

The longer the shank, the greater the leverage when the rein is activated, and the greater the pressure that is exerted on the horse’s sensitive oral tissues. The greater the pressure, the greater the pain, and that was what solved the practical problem of regulating a horse’s pace.

As the brief texts of the bit-books make clear, different bits were implemented according to different training and behavioral problems.

But Traber traces a gradual evolution moving further into the seventeenth century. Richard, earl of Newcastle, wrote in 1658:

Great pains then must be taken to make a horse fear his rider, that so he may obey out of self-love, that he may avoid punishment. A horse’s love is not so safe to be trusted to, because it depends on his own will; whereas his fear depends on the will of the rider, and that is being a dressed horse. But when the rider depends on the will of the horse, it is the horse that manages the rider. Love then is of no use; fear does all.

Obviously this sounds rather horrific, but there is something to be said about Newcastle's emphasis on fear. He's thinking about the horse's spirit, temperment, and (as is evident elsewhere in the treatise) thoughts:

[The horse] is wise and subtile: for which reason man ought carefully to preserve his empire over him, knowing how nearly that wisdom and subtilty approaches his own.

The methods of training are still abusive, but there's more of a sense of a possible relationship--even if it's one of pure domination.

It's in the 18th century--the decades after Knight rode and wrote--that Traber sees training manuals advocating a more cooperative relationship. But there is still, she notes, absolutely no sense anywhere of a pet-type relationship.

This prescriptive advice is borne out in later diaries. Caroline Barnes Crosby's fascinating diary/memoirs of New York to Utah, and Utah to California, from the mid-19th century moves a step beyond Knight in terms of her willingness to portray affection for horses. But there is still a profoundly utilitarian sense. In the middle of a rough New York winter, she writes:

We waited one day for the snow to settle a little, and then set forth towards Lake Erie, found the snow very deep, in some places. Mr Crosby walked nearly all the way; our pretty black horse began to get thin, and look sober.

Crosby's horse doesn't have a name, but she mentions it affectionately. And her description of its struggles goes a smidge beyond Knight's "and it almost died." It's not a fluke. In 1836, she wrote:

We found the roads almost impassable, the mud was up to the horses knees. We had a hard time, was nearly a week going 100 miles. Our horse's breast became very sore. It gave me very unpleasant feelings to see him work in such misery.

She portrays herself empathizing with the horse!

But at the same time, horses were still a utilitarian possession. In 1848, her family encountered a group of Sioux riders "dressed in very spendid indian style" (...you think?). She writes that they traded a little bit and "swaped horses" [sic]. No detail, no description, no drama.

There still isn't a sense of "horses as pets." And in fact, even in 1976, anthropologist Marshall Sahlins could remark that while the human-dog relationship resembled one of family, horses were traditionally treated more as servants or "nonkin" (friends?) even when they had personal names and " we are in the habit of conversing with them as we do not talk to pigs and cattle." But even before horses ceased to be a primary mode of transportation, we can trace a long evolution towards a relationship closer to pets or friends than servants or beasts.

So I can’t answer this question for all periods. However, I can shed light into this from the perspective of the 18th century.

Horses for much of Americans during this period were seen as living tools that were needed in order for agrarian survival. Until 1790, at least 95% of Americans lived on farms or small villages, not in cities. Agriculture, whether it was cash crops (like tobacco) or food, horses played an intricate part of life for farmers who needed to transport their goods from their farms/ranches/plantations and to ports. Horses and other animals like oxen and mules helped play important roles during this period, especially in the middle colonies, like Maryland.

In Maryland, the number 1 animal used for crop transport were horses. This was especially true for small scale farms (farmers who owned less than 50 acres of land), which actually made up more than 50% of the occupations in the colony by 1775. In Maryland specifically, it was common for farmers to lend or rent their horses to their neighbors. Sources show that religious communities like Quakers, Methodist, and even Catholics (who made up about 11% of the states population) were more likely to let those in their own communities borrow their horses than outsiders. Instances of this can be found all over the place, with people borrowing horses to transport livestock or even lending them to someone to make longer distance journies.

Confiscation of animals like horses also became a weaponized tool by the Patriot government in Maryland in 1777 when groups, like Quakers, refused to participate in militia musters or pay war related taxes. As punishment, the Maryland General Assembky authorized its agents to seize horses and hold them for ransom against Quakers, which happened over 100 of times between 1777 — 1881. Horses at this time were incredibly expensive, often costing over £20, but if you adjust for wartime inflation, would be worth somewhere between $4000 to $6000 today.

I don’t have sources to show one way or another if people treated their animals the way 20th century folks treated their pets, however, I can say that farmers spent a lot of money and care taking care of their horses throughout this period.

Sources for most of this can be found in:

Aglietti, Jason B. The Friends They Loathed: The Persecution of Maryland Quakers During the Revolutionary War University of Maryland Baltimore County & Proquest LLC. 2018