 
Academic dress has a history in the United States going back to the colonial colleges era. It has been most influenced by the academic dress traditions of Europe. There is an Inter-Collegiate Code that sets out a detailed uniform scheme of academic regalia that is voluntarily followed by many, though not all institutions entirely adhere to it.
Elements.
Gowns and robes.
Bachelor's and master's gowns in the United States are similar to some of their counterparts in the United Kingdom, particularly Oxford. The main differences are that the bachelor's gown is designed to be worn closed and that the sleeves of the modern gown are square at the end instead of pointed as the Code calls for. The master's gown sleeve is oblong and, though the base of the sleeve hangs down, it is square-cut at the rear part of the oblong shape. The front part has an arc cut away, and there is a slit for the wrist opening (which before 1960 was located at the elbow as on British gowns), but the rest of the arc is closed. The shape is evocative of the square-cut liripipe incorporated into many academic hoods. The master's gown is designed to be worn open or closed.
Doctoral gowns are typically black, although some schools use gowns in the school's colors. The Code calls for the outside shell of the hood to remain black in that case. Doctoral gowns have bell sleeves with three velvet bands on them and velvet facing on the front. The Code calls for the gown trim to be either black or the color designated for the field of study in which the doctorate is earned, with the proviso that the Doctor of Philosophy (Ph.D.) degree uses the dark blue velvet of philosophy regardless of the field studied. (For example, a Ph.D. in theology would wear velvet gown trim in dark blue, a Doctor of Theology (Th.D.) would wear scarlet trim, or either might choose black.) Some gowns expose a necktie or cravat when closed. They are designed to be worn open or closed in the front.
Members of a university's governing body, regardless of their degrees, are entitled to wear doctor's gowns, faced only with black velvet and black velvet bars on the sleeves. However, their hoods ("see", below) may be only those of the degree actually held by the wearer (or one specially prescribed by the institution). The color standardization for the outside shell of the hood as black provides flexibility of use and helps facilitate this practice.
Hoods.
The hood's coloring and size represents the type and subject of degree earned, as well as the institution from which it was awarded. Though no shape is specified in the Code, American bachelors and masters usually wear the Wales simple shape ([s5] in the Groves classification system) with a split salmon cut; doctors wear the same shape but with "panels" attached to the sides.
Candidates may have the hood ceremoniously placed upon them, as is done at some British universities, or a college or school may "self-hood" "en masse" at the appropriate time during the ceremony. Additionally, the Code allows for the wearing of the hood into the commencement ceremony as part of the academic procession, but only if neither of the two procedures above are being employed. The Code also states: "It is quite appropriate for the bachelor's gown to be worn without a hood." Many institutions, particularly larger ones, have therefore dispensed with the bachelor's hood at commencement ceremonies altogether, though a graduate is still entitled to wear one once the degree is conferred. Both honorary and earned doctoral degrees are very often conferred by the highest academic officer of an institution bestowing the appropriate hood at the podium, regardless of the procedure being followed for other candidates at the ceremony.
Only one hood should be worn at any given time. The regalia indicating the highest degree attained is usually worn, though the Code seems to allow for a graduate to revert for some occasion to the entire academic costume of a lesser degree earned. Those who hold multiple degrees of the same level (i.e. more than one master's or doctorate degree) may wear at any given time the regalia, in its entirety, of any one degree earned. The Code does not allow for 'mixing-and-matching.' The one exception is for officers of the academic institution who, while wearing a doctoral gown of the University being served, may display one hood from any degree earned from any institution (see "Gowns and robes", above).
Headwear.
Headwear is an important component of cap-and-gown, and the academic costume is not complete without it. The headwear may vary with the level of academic achievement and, to some extent, on the individual academic institution's specifications.
There is at some colleges and universities a practice of moving the tassel from one side to the other on graduating, but this is a modern innovation that can be impractical out of doors due to the vagaries of the wind. However, this mark of transition to graduate status has the benefit of taking less time than more traditional indicators such as the individual conferring of the hood or a complete change of dress part-way through the ceremony (as at Oxford in the United Kingdom). In such universities it is common for undergraduates to begin the commencement ceremony with their tassels on the right. Switching the tassel to the left may be done individually or as a group. For doctoral and masters students, the tassel commonly begins and remains on the left.
Other adornments.
A number of other items such as cords, stoles or aiguillettes representing various academic achievements or other honors are also worn at the discretion of some degree-granting institutions. The Code disapproves of their use on or over academic regalia, saying that"...shoes and other articles of visible apparel worn by graduates should be of dark colors that harmonize with the academic costume. Nothing else should be worn on the academic gown."Apparel and tokens representing awards and honors are not considered a component of academic dress, not only because the Code suggests avoiding them, but also because (a) they are often worn without the defining cap and gown, and (b) they are usually not worn by a graduate with academic robes after the commencement year in which the honor was awarded. Nevertheless, they are often seen with academic regalia in the United States, and are therefore mentioned here.
Intercollegiate colors.
The colors allocated to the various fields of learning have been largely standardized in the United States by the Intercollegiate Bureau of Academic Costume, and accepted by the American Council on Education in its "Academic Costume Code." The color assigned to a given hood trim and/or tassels and—where appropriate—gown facings, should be as closely related as possible to the field studied. For example, one who has earned a degree in animal husbandry would wear the maize of agriculture, as no color is specific to the subject of animal husbandry, and it is generally included within the broader field of agriculture. Less simply, mathematics is traditionally among the liberal arts, which are represented by white, but can also be considered a formal science, represented by golden yellow for science.
The codified colors associated with the different academic disciplines are as shown below:
The code calls for a graduate to display the color of the subject of the degree obtained, not the degree itself. For example, if a graduate is awarded a Bachelor of Arts (BA) degree in business, the trimming should be drab, representing commerce/accountancy/business, rather than white, representing the broader arts/letters/humanities; if the BA were in economics, the trim would be copper; if in environmental studies, it would be russet, and so on. If the BA were in a language, a subject within the humanities and not otherwise assigned a unique color, the velvet would indeed be white. Similarly, if a Bachelor of Science (BS) degree is awarded for physics, the velvet trim should be golden yellow, representing physics as one of the natural sciences; however, if the BS were in engineering, the trim would be orange, or if in education, the trim would be light blue. The same method is true of master's degrees and doctorates: a Master of Public Administration in Science and Technology should show trim of golden yellow for science, not peacock blue for public administration; conversely a Master of Science in Public Administration should display peacock blue trim for public administration and not golden yellow for science.
Additionally, it is problematic when a field of study that does not have its own color assigned to it has been considered to be included in more than one discipline, which are represented by different colors. For example, history has traditionally been considered as among the humanities, represented by white, but is also considered a social science, which can be represented by golden yellow. This is often addressed by an academic institution allowing the degree earned to influence - but not "determine" - color assignment. For instance, a Bachelor of Arts graduate in history might display white, while a Bachelor of Science graduate in history at the same institution could properly display golden yellow, and "vice versa". This then can create confusion in the first instance by appearing to display colors based on the degree earned rather than, as stipulated in the Code, the academic field studied.
In 1986, the American Council on Education updated the Code and added the following sentence clarifying the use of the color dark blue for the Doctor of Philosophy degree, which is awarded in any number of fields:"In the case of the Doctor of Philosophy (Ph.D.) degree, the dark blue color is used to represent the mastery of the discipline of learning and scholarship in any field that is attested to by the awarding of the degree, and it is not intended to represent the field of philosophy."The doctorate other than the Ph.D. will be represented by the colors indicated above. For example, the Doctor of Education (Ed.D.) in Public Health should display salmon pink for public health, not light blue for education, and the Doctor of Public Health (DrPH) in Public Administration should display peacock blue for public administration, not salmon pink for public health. The Doctor of Engineering (D.Eng.) degree, if no further specialization was made, should be represented by orange, and the Doctor of Ministry (D.Min.) by scarlet if no further specialization, etc.
History.
Colonial period.
The practice of wearing academic regalia in what is now the United States dates to the Colonial Colleges period, and was heavily influenced by European practices and styles. Students at the College of New Jersey (now Princeton University) and at King's College (now Columbia) were required to wear their "college habits" at all times starting in 1755 at Princeton and in 1763 at Columbia. Shortly after the beginning of the nineteenth century, however, academic dress was rarely worn on a daily basis, according to contemporary sources.
19th century.
After the American Civil War, academic dress was generally only worn at ceremonies or when representing the institution, although in some instances the practice has persisted, such as at , where members of one student society continue to wear the gown to class.
Although universities that adopted academic dress assigned specific meanings to them, there was no consistency among the various sets of rules. For example, when the University of Pennsylvania adopted its academic dress statute in April 1887 it abolished hoods. Instead, it assigned eight faculty colors that were shown on the gowns’ yokes.
Columbia adopted an academic dress statute in December of that year. It included the first known American inclusion of the three velvet stripes on the sleeves. Both doctors and masters wore black gowns with sleeve stripes and facing; for masters the velvet was always black, and for doctors the velvet was always purple. Columbia also approved a scarlet gown for doctors’ use on “festal” occasions. Earlier, three stripes adorned the sleeve of a gown depicted in an invitation to Class Day ceremonies at Columbia in 1865.
When New York University adopted its own academic dress in 1891, like Columbia it added the three sleeve stripes but permitted them to be worn in the university’s faculty colors. It also adopted the Edinburgh shape ([s4] in the Groves classification system) for its hoods. Although NYU gave up this shape when the Code was adopted, Harvard adopted it for all its graduates in