Arguably, the most useful of Google’s specialty search areas is that devoted to the U.S. government. Actually, this distinct search engine is both larger and smaller than the name implies. This engine is global in reach. At the same time, it reaches below federal government sites to the state and municipal level.

You might think that this entire search engine merely replaces the site:.gov operator:keyword combination. Not so. In fact, site:.gov remains quite useful in the UncleSam search because the results pages dish up a hearty mix of gov, mil (for military), and com sites that bear some relation to government, public policy, law, defense, and other fields of administration, the judiciary, and the legislature. All domain extensions are represented here.

The best way to get a feel for the blend of results you get in the U.S. government search is to throw in some keywords and let it rip. Don’t think too hard about it — any keywords will do. Try generic, common words that you’d use in a general Web search, such as internet or music or paris vacation. Or, choose newsy words such as bush or terrorism or treaty.

Many related domains are too numerous and related to list, such as state government sites and the sites of individual House members.

These searches display sites of agencies and members of congress, in addition to more general information pages.

All the specialty search engines recognize the same search operators you use in a normal Web search. I often use the filetype operator to search for PDF files in the U.S. government area, plumbing a rich trove of Congressional hearing transcriptions, court judgments, and other official documents that are customarily posted online in PDF format. Using filetype:pdf transforms any search; try adding it after any keyword string. For example:

The intitle and allintitle operators also work well in UncleSam searches. In fact, combining the power of those operators with the filetype:pdf combination is particularly fruitful because PDF files are usually titled so carefully — far more carefully than Web pages. Get specific with the title words. These examples have worked well to sharply narrow results:

The preceding examples also work nicely — and quite differently — without the filetype:pdf addition.