The first Earth Day celebration was held April 22, 1970, and was founded by former Wisconsin senator Gaylord Nelson.
The holiday is meant to increase awareness of the earth's natural environment.
Environmental groups held events worldwide that focused on environmental issues such as climate change, increased usage of renewable resources and pollution.
Several groups across the Houston area hosted Earth Day activities as well.
The Children's Museum hosted an Earth Day Extravaganza with crafts, activities, live animals and plants to take home, plus presentations by the Texas Wildlife Rehabilitation Coalition and the Texas Wildlife Association.
Residents in Sugar Land enjoyed live music, eco-friendly activities and games for kids at their Spring Concert in the Park Earth Day Celebration. The event was held at Oyster Creek Park on Highway 6.
Writers in the Schools presented Earth Day poems, stories and essays from 30 Houston ISD students Sunday at the Houston Arboretum and Nature Center on Woodway Drive.
And the Houston Zoo hosted the second day of their weekend-long Earth Day celebration. Sunday's events included a maze where children had to make the right choices about recycling to reach the end.