The Constitution is very clear about who gets to spend taxpayer money. Section 9 states that "No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law."
In other words, Congress, which makes the law, also controls the ledgers. Now, how they're to spend that money is far less structured, and for much of American history, it was pretty loosey-goosey.
Using the process called "regular order," 12 spendings bills (on things like agriculture and military and education) move through the House and Senate appropriations committees annually. This is the budget process.
Tucked inside those budget bills are something called earmarks.
They can take two forms, reports ThoughtCo. First, explicit "hardmarks," "found in the actual text of legislation," meaning "spending provisions are legally binding."
The other, more subtle form is a "softmark," "found in the reports of congressional committees on legislation," and "while soft earmarks are not legally binding, they are often treated as if they were during the legislative process."
Whether hard or soft, the marks direct money to members' districts. They could set aside millions in funding a railway upgrade in one state or facility improvements in a certain city. These are vital functions.
Then again, as the Heritage Foundation points out, the process could result in $50,000 for "a tattoo-removal program in San Luis Obispo County" or $270,000 for "an effort to combat 'goth culture' in Blue Springs, MO."
Throughout history, these super-specific earmarks often made a big difference in gaining congressional members' support for passing the larger budget. While the earmark was officially banned in the 2011 fiscal year, they still slip through in a less overt form.
The Congressional Research Service explains that the final version of spending, written by a House-Senate combined committee, usually replaces the full text of the previous bills passed by the respective chambers. Select all, delete and then copy and paste the new text.
This new combo bill often contains financial prizes for pivotal members' districts. Since House Rules mandate that any earmark is publicly disclosed, members can waive that requirement to avoid embarrassment. If a budget hawk objects, they can get 20 minutes of debate and then the bill is on the move again.
By hook or by crook, hard or by soft, specialty earmark spending survives just like any well-adapted creature of Washington.
