Her final text contained just a single word, but it haunts Jean Hanlon's (pictured) family to this day. 'Help', the message read.

National Parks are some of the most popular vacation destinations in the US and peak season is right around the corner.

They saw a combined 312 million visitors last year and the demand is showing no signs of slowing down this summer. There are 63 National Parks across the country and they are at their busiest between July and September.  

Now some require reservations to deal with the huge numbers of people visiting where travelers have to book ahead to enter certain parks and areas or drive through. 

There are seven parks where you have to make a prior booking which can be made on the recreation.gov website or using its mobile app. 

Some National Parks have turned to a reservation system to deal with the huge numbers of people visiting where travelers have to book ahead to enter certain parks, areas

Some National Parks have turned to a reservation system to deal with the huge numbers of people visiting where travelers have to book ahead to enter certain parks, areas

Some National Parks have turned to a reservation system to deal with the huge numbers of people visiting where travelers have to book ahead to enter certain parks, areas

Zion National Park

Zion National Park in Utah was the third most visited national park last year with more than 4.5million visitors. 

It decided to make use of a reservation system again to deal with the huge numbers of travelers.

Bookings are not needed to enter the park but are required for those who want to hike up Angels Landing.

There is a season lottery which costs $6 a person or a $3 permit, available the day before. 

Zion National Park in Utah was the third most visited national park last year with 4.5million visitors and has decided to make use of a reservation system again to deal with the numbers

Zion National Park in Utah was the third most visited national park last year with 4.5million visitors and has decided to make use of a reservation system again to deal with the numbers

Zion National Park in Utah was the third most visited national park last year with 4.5million visitors and has decided to make use of a reservation system again to deal with the numbers

Glacier National Park

If you are driving through Glacier National Park in Montana to visit Going-to-the-Sun Road, you need a vehicle reservation between 6am and 3pm.  

The ticketing system was introduced on May 26 and will last until September 10 and vehicles need a three-day reservations to access the park’s entrance on the west. 

Those heading to the North Fork area of the park need a one-day reservation.

And between July 1 and September 10, from 6am to 3pm, the St. Mary entrance to Going-to-the-Sun Road, Many Glacier and Two Medicine will all require reservations.

If you are driving through Glacier National Park in Montana to visit Going-to-the-Sun Road, you need a vehicle reservation between 6am and 3pm

If you are driving through Glacier National Park in Montana to visit Going-to-the-Sun Road, you need a vehicle reservation between 6am and 3pm

If you are driving through Glacier National Park in Montana to visit Going-to-the-Sun Road, you need a vehicle reservation between 6am and 3pm

Rocky Mountain National Park

The Rocky Mountain National Park in Colorado requires one of two ticket options to visit between May 26 and October 22.

The first option is to access Bear Lake Road Corridor and the park between 5am and 6pm whereas the second is needed to access the park between 9am and 2pm. 

Bookings started at 8am on May 1 and are open on the first day of each month for entry the following month. 

But around 40 per cent of tickets are available the day before a visit at 5pm.

The Rocky Mountain National Park in Colorado requires one of two ticket options to visit between May 26 and October 22

The Rocky Mountain National Park in Colorado requires one of two ticket options to visit between May 26 and October 22

The Rocky Mountain National Park in Colorado requires one of two ticket options to visit between May 26 and October 22

Shenandoah National Park

Virginia’s Shenandoah national park started reservations on March 1 and it will run up until November 30.

There are 800 tickets are available to visit the Old Rag Mountain area every day. 

And there are 400 tickets released for park reservations 30 days and five days prior to a visit. 

Virginia¿s Shenandoah national park started reservations on March 1 and it will run up until November 30

Virginia¿s Shenandoah national park started reservations on March 1 and it will run up until November 30

Virginia’s Shenandoah national park started reservations on March 1 and it will run up until November 30

Arches National Park

A reservation to visit Utah’s Arches national park between 7am and 4pm is a strict requirement. 

The booking system began on April 1 and will last up until October 31 with tickets accessible on the first day of each month at 8am for visits three months in advance. 

But a limited amount of tickets are released a day before for arrivals at 6pm.  

The reservations are free but require a non-refundable $2 processing fee.

A reservation to visit Utah¿s Arches national park between 7am and 4pm is a strict requirement

A reservation to visit Utah¿s Arches national park between 7am and 4pm is a strict requirement

A reservation to visit Utah’s Arches national park between 7am and 4pm is a strict requirement

Haleakala National Park

The Haleakala National Park in Hawaii on the island of Maui has had a reservation system in place for years. 

It is famous for beautiful sunrise views which makes it an incredibly popular place to go.

Those lucky enough to visit need a vehicle reservation, which costs $1, to enter the park between 3am and 7am. 

But those who want to enter outside of these hours can enjoy the park without a prior booking. 

The Haleakala National Park in Hawaii on the island of Maui has had a reservation system in place for years

The Haleakala National Park in Hawaii on the island of Maui has had a reservation system in place for years

The Haleakala National Park in Hawaii on the island of Maui has had a reservation system in place for years

Acadia National Park

Acadia National Park in Maine has reverted back to its reservation system for vehicles heading to the Cadillac Summit Road section of the park between May 24 and October 24. 

It is a popular part where drivers can enjoy a three-mile ‘scenic drive to the top of the highest peak’ for breathtaking views. 

A total of 30 per cent of vehicle passes can be obtained 90 days before a visit while the rest are put up at 10am two days in advance. 

Each pass costs $6 but those who want to enter another area of the park or are not in a vehicle do not have to make a prior booking. 

Acadia National Park in Maine has reverted back to its reservation system for vehicles heading to the Cadillac Summit Road section of the park between May 24 and October 24

Acadia National Park in Maine has reverted back to its reservation system for vehicles heading to the Cadillac Summit Road section of the park between May 24 and October 24

Acadia National Park in Maine has reverted back to its reservation system for vehicles heading to the Cadillac Summit Road section of the park between May 24 and October 24