During 1790-1800, was it legal to pay workers using whiskey?

Not only was it legal, but until the 1820s workers across the country expected their employers to pay them part of their wages in whiskey. The wage labor system was not yet well developed. Instead, historians like Paul Johnson refer to a "household economy" in which apprentice and journeymen mechanics were treated as members of the household of the master craftsmen, who provided his "employees" with room, board, training, spending money--and whiskey.

Here's Johnson on the expectation that drink be provided both at home and on the job:

Among laborers and building tradesmen, the dram was an indispensable part of daily wages. And in the workshops, drinking was universal. Not only independent craftsmen and shoemakers hidden away in boardinghouses, but men who worked directly under churchgoing proprietors drank on the job and with their employers.

This was all part of a traditional, paternalistic system of labor control:

Liquor was embedded in the pattern of irregular work and easy sociability sustained by the household economy. It was a bond between men who lived, worked, and played together, a compliment to the unique kind of domination associated with that round of life. Workmen drank with their employers, in situations that employers controlled. The informal mixing of work and leisure and of master and wage earner softened and helped legitimate inequality. At the same time drunkenness remained within the bounds of what the master considered appropriate. For it was in his house that most routine drinking was done, and it was he who bought the drinks.

The maturation of wage labor disrupted the paternalistic relationship between master and workmen:

That changed abruptly in the 1820s. Masters increased the pace, scale, and regularity of production, and they hired young strangers with whom they shared no more than contractual obligations. The masters were becoming businessmen, concerned more with the purchase of labor and raw materials and the distribution of finished goods than with production itself. They began to absent themselves from the workshops. At the same time they demanded new standards of discipline and regularity within those rooms. We shall see that those standards included abstinence from strong drink.

With drink now a "social problem," we see the sudden development of two new social phenomena in the U.S. On the side of capital, the middle classes immediately organized the temperance movement in order to increase the productivity of their employees. On the side of labor, the working class developed "the working class pub" as a new social setting where workmen could talk and drink without interference or surveillance by their employers.

Source: Paul Johnson's excellent A Shopkeeper's Millenium

For commodity whiskey prior to transportation: 50c a gallon http://www.discus.org/heritage/distillery_faq/ For 4 distilled whiskey $1 a gallon.

Assuming that Whiskey could be locally produced in most areas, this seems like a good price.

Now let's get a labour price: http://www.measuringworth.com/datasets/uswage/result.php# $0.02 an hour for 1790 for "production workers." I think this is a reasonable assumption

Assuming a 6 and a half day week of a 12 hour day (not unreasonable, see Thompson, Making Engels, 1844 etc.) that gives us a weekly of 78 hours.

But of course we need to subtract Saint Monday. (Thompson, Time work discipline and industrial capitalism, P&P): 66 hours.

66x0.02= 1.32 a week.

Or between 2 gal 3 pints and 1 gal a week.

Was it legal? Yes. Employers could use their power to force payment in scrip or truck wherever unions didn't exist.

Yes. Or perhaps "undefined". Was it legal? Where? Who would have passed a law forbidding the practice? Why would they pass such a law? Why wouldn't you pay someone in whiskey?

Consider two things -

1. With all due respect to @Samuel Russel, the early government was concerned with labor law only where it concerned servitude. The division between North (commercial, anti-slave) and South (Vehemently anti-commercial, pro-slave) was far more important than the distinction between employer and employee.
2. Nobody had money - the economy was based on barter, and whiskey is an excellent barter good.

Immediately after the American rebellion, and most especially during the period of the Articles of Confederation, (1777 to 1789), the national government was uninterested in labor law. Controversies such as the role of slavery, the pre-eminence of the North and South, the role of commerce vs agriculture, the right to Navigate the Mississippi, or the relative evils of France and Britain were dominant issues. State governments were relatively stronger than the Federal government (by design), and each state government had different opinions about the future of the country.

The new US was an economic disaster. Government officials abandoned their posts and refused to be re-appointed because the government couldn't pay them. State governments were in severe debt and many were close to default. As a result of these factors, there simply wasn't money with which to pay people. Almost everyone used scrip or barter. Being paid in whiskey was no more unusual than being paid in tobacco, or bacon, or any other good. If anyone had tried to make it illegal, they probably would have faced laughter rather than revolution.

For years, the US economy was based on shipping tobacco to England, and most commerce was conducted in tobacco for years - merchants would issue and accept scrip in the form of tobacco that was payable only if the tobacco was conveyed to England and sold there.

West of the Appalachians (where the colonies had been forbidden to settle, and where the "national government" had a very tenuous presence) were particularly poor in specie. People turned to barter. West of the Appalachians, the dominant industry was farming, but the country didn't yet have the transportation infrastructure necessary to send farm goods to market. The one good that could be transported over long distances was distilled spirits and whiskey.

Any frontier farmer who raised more grain than he could eat or feed to his livestock could distill whiskey at home. If he didn’t own a still, he found a neighbor who did and gave him a portion of the whiskey as payment. A bushel of corn made about three gallons and was worth more in liquid form.

Williamsburg

note that this was not an employer/employee relationship, but barter between merchants

Whiskey is a natural medium of exchange for barter. It is stable, divisible and transports well. Why wouldn't you pay in whiskey?

Update: @Samuel Russell points out that I neglected to address the nearly pathological fear of scrip in the new colonies. I thought I had mentioned that, but I see that I did not. Then I tried to find good sources to explore the topic, and I can't (yet) find any that are succinct.

As sure as death all mortals trips, THOUSANDS will rue their faith in scrips

A Maryland paper as quoted in "The Opposition Press of the Federalist period"

Well managed scrip might have provided an alternative to barter the trick was finding someone with the discipline to manage the scrip. Nobody understood monetary theory or inflation, so nobody had the intellectual tools needed to effectively manage scrip. The new states (particularly Rhode Island) had very bad experiences with scrip. Speculators bought up scrip during an inflationary period and a small minority found themselves in effective possession of the entire state of Rhode Island. It is difficult for modern minds to appreciate just how deeply the new Americans distrusted scrip. Pauline Maier's "Ratification: the People debate the constitution" is probably the best source I've read on this, although anything about Jefferson will reveal the level of irrational fear. (OK, perhaps Jefferson's as America's leading deficit spender was justified in fearing commercial interests, but that is a separate topic).