This can't be helped - there are more animals than homes for them.
However, with updated facilities, innovative programs, dedicated volunteers and community awareness - things are getting better.
Under California law, shelters are mandated to hold animals 72 hours, said Bill Harford, president and CEO of Inland Valley Humane Society & S.P.C.A.
However, Inland Valley adheres to The Hayden Law, which, according to www.news10.net, stated shelters hold animals four to six days before they can be killed.
After the waiting period, each animal is reviewed by medical and behavioral professionals to determine its medical, physical and emotional conditions to determine adoptability.
"It all depends on the animal," said Harford, who has worked at Inland Valley for more than 35 years. "So many factors go into determining what is an adoptable animal and what is not. Sometimes a dog can come into the shelter very adoptable, but can go stir crazy from being in the shelter and become not so adoptable. We hold them as long as they're healthy and engaged."
Adding perspective, Harford shared some astonishing numbers.
In 1979, Inland Valley served Pomona, Claremont, La Verne and San Dimas with a total population of 225,000 and handled 35,000 dogs and cats a year - mostly dogs.
Today, Inland Valley contracts with 10 cities along with the unincorporated sections of San Bernardino County serving more than four times the population, but less than half as many animals.
"We have taken a pro-active approach to animal care and control," Harford said.
In the past four years, adoption numbers have stayed between 2,500 and 3,000 animals per year.
And the shelter's numbers are decreasing.
Thanks to large spay and neutering efforts, partnerships with other animal groups and shelters, committed staff members and volunteers.
The Upland Animal Shelter is also seeing positive changes, but not without vigilant efforts.
Jon Knowlton, Upland animal services supervisor, agrees with Harford. He was also proud of Upland's progress, especially in the shelter's intake of stray cats.
"Thanks to a grant from PetSmart Charities, last year for the month of August we took in 143 stray cats; this year 55," said Knowlton, of a grant that funds the trapping, spay and neutering and release of free roaming Upland cats. "It usually takes five years to see a grant like this take effect."
In 2011, the Upland Animal Shelter took in 1396 dogs and 1,394 cats; 941 dogs and 839 cats were adopted with 17 percent of animals euthanized.
"That's a 25 percent drop from 2010," Knowlton said. "As long as a dog is healthy and adoptable we'll try and hold them, but sometimes dogs can acquire aggressive behaviors and sometimes we have to euthanize for space."
Both shelters have aggressively pursued partnerships with other shelters, rescue groups and animal advocates to reach their goals of finding forever homes for every animal.
The Rancho Cucamonga Animal Care and Services Center carried a euthanasia rate of about 12 percent in 2011.
Euthanasia rates in 2010 were at 20 percent.
The rate, which has remained stable this year, officials said, is relatively lower than other shelter euthanasia rates from shelters in San Bernardino County.
Elsewhere, the rates can be as high as Hesperia's 69 percent, according to official documents.
Adoption rates in Rancho Cucamonga have also increased by 3 percent this year, said Veronica Fincher, the shelter's director.
In 2010, adoption rates at the Rancho Cucamonga shelter were at 65 percent.
In 2011, adoption rates in Rancho Cucamonga were at 74 percent.
The Rancho Cucamonga animal shelter takes in about 5,000 animals annually.
Staff writer Neil Nisperos contributed to this report.
Reach Diana via email, or call her at 909-483-9381.