Some minimum ages, which of course vary from state to state.
Of the 38 states that have death penalty, 5 have a minimum age of 17, while the rest is about equally divided between 16 and 18 years. A minimum age below 16 is considered unconstitutional. (DPIC)
Since 1990, 19 minors have been executed in the USA, a world record. Next comes the Iran with seven executions. Of course, the USA have nearly four times as many inhabitants as the Iran.
Ages vary between 15 and 18, but 16 seems to be a good rule of thumb.
The actual "drinking age" varies from state to state, but is nowhere below 18, and 21 in the majority of states (31). Minimum age for purchase and public possession is 21 in all states due to federal regulations. (ICAP)
This is a bit confusing. Federal law makes the depiction of minors (under 18) in sexual conduct or or in sexually suggestive poses a crime, as well as making "adult" material available to minors or trying to access "adult" material as a minor. The actual "age of consent" varies between 16 and 18 in the different states and may even be 14 in South Carolina, but there is a general tendency to effectively raise this age to 18 with various by-laws. A U.S. citizen or permanent resident havin consensual sex with someone under 16 abroad commits a felony even if local laws allow it, unless the difference of ages is under four years. (ageofconsent.com)
Laws regarding gun ownership are too intricate to be listed here. Federal regulations provide 18 for owning hand guns, and no age limit for long guns, but can obviously be superseded by state legislation. In Montana, for example, the minimum age for buying a handgun is 14.