Webster's 1828 dictionary: Misdemeanor

Daniel Webster (edit, oops, Noah!), 1828, provides proof that a misdemeanor was not necessarily a crime:

MISDEME'ANOR, noun Ill behavior; evil conduct; fault; mismanagement.

1. In law, an offense of a less atrocious nature than a crime.
Crimes and misdemeanors are mere synonymous terms; but in common {1825} usage, the word crime is made to denote offenses of a deeper and more atrocious dye, while small faults and omissions of less consequence are comprised under the gentler name of misdemeanors
http://webstersdictionary1828.com/Dictionary/misdemeanor

High: 34. Great; capital; committed against the king, sovereign or state; as high treason, distinguished from petty treason, which is committed against a master or other superior.

It seems it would have been incorrect to refer to a misdemeanor as a 'high misdemeanor' as some during impeachment took it, as 'high crimes and high misdemeanors', since saying a 'high smaller fault of less consequence' would be sort of oxymoronic - compare with jumbo shrimp.
Addendum - jumbo shrimp is not really an oxymoron, when intending shrimp as being the shell fish. George Carlin wrong.

CRIME, noun [Latin , Gr. , to separate, to judge, to decree, to condemn.]
1. An act which violates a law, divine or human; an act which violates a rule of moral duty; an offense against the laws of right, prescribed by God or man, or against any rule of duty plainly implied in those laws. A crime may consist in omission or neglect, as well as in commission, or positive transgression. The commander of a fortress who suffers the enemy to take possession by neglect, is as really criminal, as one who voluntarily opens the gates without resistance.
But in a more common and restricted sense, a crime denotes an offense, or violation of public law, of a deeper and more atrocious nature; a public wrong; or a violation of the commands of God, and the offenses against the laws made to preserve the public rights; as treason, murder, robbery, theft, arson, etc.
The minor wrongs committed against individuals or private rights, are denominated trespasses, and the minor wrongs against public rights are called misdemeanors.
Crimes and misdemeanors are punishable by indictment, information or public prosecution; trespasses or private injuries, at the suit of the individuals injured. But in many cases an act is considered both as a public offense and a trespass, and is punishable both by the public and the individual injured.
2. Any great wickedness; iniquity; wrong.