I'm studying A Level English literature at the moment and we are reading The Great Gatsby. I have a teacher who alluded that during the time the text was written, 1925, wives were considered to be a man's property. This raised red flags for me, as I know this may be true figuratively but I want to know if that was legally the case ever in the United States, and particularly in 1925.
There were limited instances of the institution of wife selling in Britain in the early modern period, but this practice was never transferred to the United States and received as part of its common law. The institution of wife selling had been abolished long, long ago in 1925 in Britain and had never existed in the U.S., and was quite rare even when it had existed in Britain (where it functionally served as a poor man's alternative to divorce if a substitute husband could be located for an unfaithful or unwanted wife).
Also, even in the early English common law, a marriage only arose with a woman's consent (sometimes implied from cohabitation or pregnancy in cases of common law marriage), even though de facto arranged marriages were common. While the wedding ceremony, in part, contemplated a notion that a father sold his daughter to the groom and at some times a father actually did have veto power over his children's marriage in England (causing many elopements to Scotland), the woman actually still had to consent in England, at least in principle, to the marriage.
Married women did have greatly diminished legal rights, but they lacked important aspects of being property such as transferability. At common law, the legal status of a married woman was very different from that of an unmarried adult woman (a "femme sole"), and was more like that of a child, and the legal rights of men and women in marriage were, in general, very different.
Phoog's answer is correct in identifying the doctrine of coverture and the suspension of the legal personality of the wife upon marriage as the dominant aspect of the differential treatment of women in marriage, but I will spell out in this answer the pervasive nature of the doctrine as applied since some of the practical consequences of this general idea are not obvious.
In the most pure version of the traditional English common law, rules included the following:
Upon marriage, all property of the married woman became property of her husband instead, which the husband had sole authority to manage. A wife's earnings were her husband's property and not her own. But, trusts could be established by third parties (often a father or uncle) for the benefit of a married woman that did not become a husband's property, and her blood relations would often give a woman gifts that in the case of personalty were not always in the full control of the husband.
A married woman could not enter into binding contracts except for "necessities", and could not enter into executory contracts (i.e. contracts to be performed in the future).
There was no criminal liability for offenses other than murder committed by a husband against a wife or vice versa (e.g. rape and domestic violence of a husband directed at a wife was legal).
A husband had a right to physically discipline his wife or to hire a third-party public official to do so on his behalf and many local governments had an official whose responsibilities included physically disciplining wives at a husband's request for a scheduled fee.
Adultery was a crime and wives were generally the ones most likely to be prosecuted for it.
A wife was legally obligated to maintain her domicile with her husband and could be legally compelled (with third-party assistance if necessary) to return to it.
There was no civil liability between spouses who were one person under the law (i.e. spouses could not sue each other in court). This changed mostly in the mid-20th century. But, a husband was often held to civil liability for the acts of his wife to a similar extent to the liability he would have for the acts of his children or his dogs and livestock.
Wive could not (and still cannot in most circumstances) testify against their husbands in court on any matter.
A lawsuit of a wife against a third person would generally be brought by the husband either on her behalf or in cases such as personal injury suits for "loss of consortium" (a legal right of the man to companionship and service from his wife).
Wives generally had no right to inherit from their own families (at least for real property, inheritance of personalty in early common law England was vested in the Church of England, another part of the common law not carried over to the U.S.), and spousal inheritance rights were governed by principles of curtsey and dower (often leaving a surviving spouse a life estate in property, rather than ownership of it).
Women, in general, could not vote or run for public office or serve on juries or be drafted to serve in the military.
In the early common law era, divorce could only be secured by legislation, not by a court. A wife could, however, apply to a court for "separation from bed and board" that would leave the marriage intact, but would allow her to live at a different domicile and to have her husband compelled to support her with what amounted to alimony. This was available on grounds comparable to early 20th century fault based divorce. Custody of children and full authority over them in the event of a dispute was generally vested in a husband.
Children born during a marriage were conclusively presumed to be a husband's children even if this was highly implausible as a matter of fact, and children born outside of marriage were illegitimate and had no legal rights at all vis-a-vis their fathers.
But, in most cases, a free adult femme sole (as opposed to an indentured servant or slave) had the same legal rights as a man. In practice, this was only viable for wealthy women or self-employed women as few forms of regular employment were available to women (most commonly entering into a relationship with an employer as a domestic servant which was a bit like indentured servitude except that the servant was paid money in addition to room and board, and had the right to quit).
Also, a man could vest authority to manage the couple's estate in his wife, which would not be uncommon, particularly if the husband was away at war or on business.
Not every U.S. state followed this regime in a pure manner, but a substantial part of this regime governing the rights of married women was adopted almost everywhere in the U.S. at some point (except for the states entering the union in the 20th century).
This changed on a state by state basis, partially due to evolution of the common law, but in substantial part due to the passage of "Married Women's Property Acts" mostly in the 19th century. Remaining vestiges of this regime that were not changed legislatively by the 20th century were mostly later struck down by courts, often on 14th Amendment grounds, although removal of some of the criminal law immunities (the last of which was the marital rape exemption) was legislative and came in the later 20th century.
The 19th century was also the time period during which legislative divorce was replaced on a state by state basis with court-granted fault-based divorce, which in turn was replaced on a state by state basis in the late 20th century and early 21st century (New York State was the last to adopt no-fault divorce).
I have a teacher who alluded that during the time the text was written, 1925, wives were considered to be a man's property. This raised red flags for me, as I know this may be true figuratively but I want to know if that was legally the case ever in the United States, and particularly in 1925.
In 1925, most U.S. states had passed Married Women's Property Acts (including the states featured in the Great Gatsby), and court-granted divorces on the basis of fault were available (although rare), but there were still many residual aspects of the early common law regime in place. Divorce was, in practice, hard to obtain and expensive.
Adultery was a crime and marital rape was not. A husband was generally immune from criminal liability concerning a wife, although often this would be in the form of a privilege similar to the self-defense privilege for "reasonable discipline of a wife" similar to the exclusion today for reasonable discipline of children, rather than an absolute immunity from liability.
Civil liability exemptions would have still existed. Many "heart balm torts" (which allowed civil remedies for adultery for example against the other man) would have been in existence (a few U.S. states still have them), which effectively gave a husband some "property rights" in his wife's fidelity that had to be observed by third parties. But, by 1925 many states were starting to legislatively repeal cause of action for "heart balm" torts.
Inheritance laws would not have been gender neutral but would not have so decisively disfavored married women either.
In divorces, the "tender years doctrine" which awarded children under 12 to wives and older children to husbands would have been in the process of development.
Some of the presumptions about a husband's authority over a wife's property and a woman's obligation to share a domicile with her husband would have been widely understood even though the legal basis for this living law would have been eroding and it would be outrageous in that time period to use third-party physical force to compel a woman to return to a domicile or to discipline a wife.
In short, while a wife was not a husband's property in 1925 and had many more legal rights than she did in the early common law era, a wife still had many legal disabilities at that point in time and in the living law in the minds of ordinary people, her rights were even more diminished than the relatively progressive legal rights that she had under relatively newly enacted legislation. The mindset of wives as property, while not strictly true, still have a residual influence and relevance in the form of residual legal disabilities of married women.
Of course not. There may be legal systems in which wives were considered their husbands' property, but that was never the case in the US.
As in many legal systems, wives at times had little or no legal personality independent of their husbands, but that isn't the same as being the husband's property. An example illustrating the fact that a wife is not her husband's property is the fact that a husband could not sell or otherwise "dispose of" his wife.
For more on wives' lack of independent personality, see the Wikipedia article on coverture, which includes the classic Blackstone quote:
By marriage, the husband and wife are one person in law: that is, the very being or legal existence of the woman is suspended during the marriage, or at least is incorporated and consolidated into that of the husband: under whose wing, protection, and cover, she performs every thing; and is therefore called in our law-French a feme-covert; is said to be covert-baron, or under the protection and influence of her husband, her baron, or lord; and her condition during her marriage is called her coverture. Upon this principle, of a union of person in husband and wife, depend almost all the legal rights, duties, and disabilities, that either of them acquire by the marriage. I speak not at present of the rights of property, but of such as are merely personal. For this reason, a man cannot grant any thing to his wife, or enter into covenant with her: for the grant would be to suppose her separate existence; and to covenant with her, would be only to covenant with himself: and therefore it is also generally true, that all compacts made between husband and wife, when single, are voided by the intermarriage.
It's worth noting that this area of law belongs to the states in the US, so the details depend on the couple's jurisdiction, but the present question can be answered generally, and accurately, in the negative.