The list and frequency of occupations

farmer / planter: 102 - from 1600s through 1800s; full-time or  with another profession.
grist mill owner: 10
tavern or inn keeper: 8
carpenter: 6
mariner: 5
minister: 4
merchant: 4
tanner: 3
teacher: 3 [one 20th century]
iron worker: 3
coastal trader: 3
saw mill owner: 3
farmstead manager: 2
clerk: 2
stone mason: 2
teamster: 2 [late 1800s as urbanization set in]
blacksmith: 2
doctor: 2
cooper: 2
farm laborer: 2

One time jobs:

wheelwright                      papermaker
coal miner                         hunter
tailor                                  attorney
sales agent                         farrier
lead miner                         housewright
land agent                         cattle tender
distiller                              tray maker
chandler                            vintner
supercargo                        livestock dealer
brickmaker                       turpentine maker

The majority of the above professions covered the 17th, 18th and 19th centuries. A shift came during the last half of the 19th century as farmers sold their land to look for opportunities in America's growing cities.

Four of the above occupations were tied to the sea from about 1600-1815: mariner, chandler, supercargo and coastal trader. 10 total.

For those of you with Huguenot or Walloon ancestry: The majority of the male immigrants were tied to the cloth or fabric trades. Weaver, threadtwister, camletmaker and other jobs found in that business will show frequently as careers in The Netherlands as the Huguenots and Walloons prepared for trips to New Netherland, Virginia, the Carolinas, etc. These people became farmers, planters, merchants, traders, etc. in the colonies.

Almost exclusively 20th century:

tool and die maker: 2
solicitor: 2, collector, canvasser: 1 each [probably the same job]
cornice maker: 1
genealogist: 1 [of course, a few other family members kept records, but most were lost]
janitor: 1
secretary: 1
veterinarian:1
federal meat inspector: 1
night watchman: 1

As you utilize city directories for your research, beware of occupational terminology. City directories cover about 1865 - present in most cases. Some large cities [NY, Philly, etc.] may date back much earlier.

The directory entry will give the person's occupation and may give the place of work. Lookout for generic terms such as mechanic or laborer. Those two cover a lot of territory. A mechanic works with his hands or machinery [carpenter, painter, smithy, etc.] Generally an auto mechanic will be listed as such. Laborer could cover almost any job. Look at entries for 4-5 years: laborer, mechanic, carpenter, carpenter, laborer - focus on the specific career: carpenter.