It's highly recommended. USA brought in some tighter restrictions on crossing the border in 2009, when the Western Hemisphere Travel Initiative came into law. And that has required Canada to follow suit.

As someone else said, to get into Canada, American tourists don't really need anything more than proof of their nationality and government issued photo ID. But it's getting back into USA that would be an issue if you don't have a WHTI-approved travel document.

The EASIEST and CHEAPEST approved travel document your grandparents could use is a passport card. It's like a passport book, but only lets you travel by land or sea to Canada and Mexico. The full passport book is better since it can be used to enter any country, and you need it to board any international flight.

Another option is the Enhanced Driver License, if their home state offers that type of license. Again, it's only good for driving or by water, not flying.

For you, if you are under 16 years old, you can still cross the border by land with just your birth certificate. But if you are older, then you need the passport book or passport card.

If you or your grandparents don't have one of the approved documents to use, you could try crossing with just photo ID and birth certificate. There is a chance that Canada's border agents will still let you in. But you can expect to get an earful when you return to USA and get stopped at the border by the CBP. I've heard that they sometimes will keep you there for hours while they "verify your identity". Eventually they let you in, but certainly not something I want to deal with at the end of my vacation. Do you?

Going by air then you need a passport.

Permanent Resident you can use your Green Card.

US Citizen over 16 going by land or sea you can use an Enhanced Drivers License, Passport Card, NEXUS card or Passport. If you are under 18 your parents will need to have a notarized letter signed by both that gives your grandparents permission to take you across the border.

It would be strongly advisable Aria. By the time you muck around with applying for Nexus, your better off with a passport. There has been changes to the cross boarder regulations, which came into effect in 2009. Both US and Canadian Boarder Services are asking to sight passports even more these days..

It does not hurt to have a passport as a formal form of identification Aria.

DO YOU?

Depends on your CITIZENSHIP.

Are you a US CITIZEN? Are your Grandparents US Citizens?

Just living in the USA does not make you a CITIZEN.

Just travelling from the USA does not make you a US Citizen.

You NEED something that allows you to enter Canada.

You NEED something that allows you to EXIT Canada. TO SOMEWHERE

Most use a Passport. There are other things you can use.You most likely do not have the other documents.

What you NEED to Enter Canada is here.

http://www.cbsa.gc.ca/travel-voyage/td-dv-eng.html

What you NEED to Exit Canada depends on where you go next. Most will go to the USA

for that you NEED to have with you in order to enter Canada

U.S. citizens can present a valid: U.S. Passport; Passport Card; Enhanced Driver’s License; Trusted Traveler Program card (NEXUS, SENTRI or FAST); U.S. Military identification card when traveling on official orders; U.S. Merchant Mariner document when traveling in conjunction with official maritime business; or Form I-872 American Indian Card, or (when available) Enhanced Tribal Card.

U.S. and Canadian citizen children under the age of 16 (or under 19, if traveling with a school, religious group, or other youth group) need only present a birth certificate or other proof of citizenship. The birth certificate can be original, photocopy, or certified copy.

WHTI does not affect U.S. Lawful Permanent Residents, who are still required to present their permanent resident card (Form I-551) or other valid evidence of permanent residence status.

Crossing a Border is more than just showing your ID Card. Canada does not have to let you in.

You are going to a FOREIGN COUNTRY: so: by car: valid passport or US passport card or NEXUS card or enhanced driver's licence. You high school ID is worth zip.

Not if you have a different WHTI (Western Hemisphere Travel Initiative) approved ID such as an enhanced driver's license. https://www.cbp.gov/travel/us-citizens/western-hem... . A regular driver's license is no longer valid for crossing a land border.

Each of you require a passport regardless of your method of entry

yes, regardless of if your leaving canada or not you need a passport, any and all boarder crossings

yes, regardless of if your leaving canada or not you need a passport, any and all boarder crossings

No ... BUT you need a passport to get back into the United States. (seriously)