If a shutdown continues, it could interrupt the Environmental Protection Agency’s work and pull workers from maintaining national parks.

If a U.S. government shutdown goes on long enough, it could throw a wrench in travel plans, potentially leading to longer airport wait times, flight delays and even cancellations.

If a facility or grounds are normally locked after hours -- such as a visitor center or gated parking lot with set opening and closing times -- they will remain closed for the duration of the shutdown. Parks without accessible outdoor areas will shut down completely.

Partisan spending disputes occasionally shut down parts of the government for a few days or a few weeks. Traditionally, "essential" workers such as military troops or air-traffic controllers are exempt from a shutdown, while visitors to national parks notice custodial workers are "non-essential" and trash piles up.

Congress didn't reach a budget deal by midnight Oct. 1, causing a federal government shutdown. Here's what it could impact.