There have always been dogs native to North America. They were not introduced into the U.S. from Another Country or continent.
1999
As a rule, Dogs come in 'HEAT' twice a year. They generally can have puppies after they are 1 year old, and every year after that. One litter a year usually. It is recommended that dogs don't get pregnant the first time they come in Heat.
Dogs come into heat every 6 months.
Most dogs come into season approximately every six months (twice a year) but for some dogs it can be one to four times a year.
over 1,000
Immigrants come to the US every year. There has never been a single year of US history in which there were no immigrants.
Over 1000 dogs.
in the year of 1528
2000
everyday
the year 1320
in the year 1581