Medieval and early modern tradition recognized only three professions: divinity, medicine, and law – the so-called "learned professions".
Major milestones which may mark an occupation being identified as a profession include:
an occupation becomes a full- time occupation
the establishment of a training school
the establishment of a university school
the establishment of a local association
the establishment of a national association of professional ethics
the establishment of state licensing laws
Applying these milestones to the historical sequence of development in the United States shows surveying achieving professional status first (note that George Washington, Thomas Jefferson, and Abraham Lincoln all worked as land surveyors before entering politics ), followed by medicine, actuarial science, law, dentistry, civil engineering, logistics, architecture and accounting.
With the rise of technology and occupational specialization in the 19th century, other bodies began to claim professional status: mechanical engineering, pharmacy, veterinary medicine, psychology, nursing, teaching, librarianship, optometry and social work, each of which could claim, using these milestones, to have become professions by 1900.
Just as some professions rise in status and power through various stages, others may decline. Disciplines formalized more recently, such as architecture, now have equally long periods of study associated with them.
Although professions may enjoy relatively high status and public prestige, not all professionals earn high salaries, and even within specific professions there exist significant inequalities of compensation; in law, for example, a corporate/ insurance defense lawyer working on a billable-hour basis may earn several times what a prosecutor or public defender earns.