Federal employment is ideal for frum Jews. Very few jobs have issues with Shabbos. If travelling, you might have to arrive early or stay late in a city (for example a Friday meeting will require spending Shabbos in that city), but you can usually find frum Yidden to stay with. You can even impress your boss by being super-frugal by preparing food in your hotel room instead of running up restaurant tabs. Since most government, for the last 80 years or so, has been on a strict five day week, Shabbos issues aren’t too common. Unlike the private sector, Federal always makes a good faith effort at religious accomodation.
Some areas are problematic. The law enforcement and the uniform services expect you to be on call 24/7, so non-medical positions in the armed forces are probably out (though civilian work is not a problem for these agencies, even in the defense department). In jobs dealing with Israel, they (probably rightly) are suspicious that anyone may be more inclined to be pro-Israel even if this conflicts with American policy (which isnt’ to say that there aren’t frum Jews working in serious positions for the NSA and the FBI).
Of course most of the good Federal jobs require living in the Baltimore-Washington metropolitcan area (which is good for yiddishkeit, and cheaper than New York), and Federal health and retirement benefits are excellent.