During the Republic of Texas, emigration into Texas (meaning, leave one's original place for another) did not rely on legal processes involved in immigration but rather on colonization, because Texas wanted land owners who would duke it out with Native people and the Mexican army. This is one of the key strategies of colonization schemes: the new land-owners, because they had a vested interest, acted as protection buffers for a government that wasn't deemed completely legitimate by the places they were colonizing.
Most of the emigration companies that formed during the Republic of Texas were beset with problems. "Successful" colonization often relied on the individual land grantees' challenges in court, not on the administrators who ran the schemes. Charles Fenton Mercer's colonization plan was no different.
Mercer's Colony, which would become parts of northeast Texas counties of Johnson, Ellis, Hill, Navarro, Grayson, Collin, Dallas, McLennan, Rockwall, Hunt, Rains, Van Zandt, Kaufman, and Henderson Counties, received permission in January of 1844 to form a separate land grant process from Peters Colony (the Republic of Texas's colonization scheme in northeast Texas). The first trouble with the colony, which named itself "Texas Association," came from squatters who simply took up residence on land designated for the colony. The second trouble came from competition with Peter's Colony, which granted 320 acres rather than Mercer's 160 acres. The third trouble derived from the Texas legislature, which did not like the fact that Houston had granted a colonization contract with Charles Fenton Mercer, a committed abolitionist. Further, legislators argued that private land granting companies did not benefit the state, so why allow them to exist? After 1845, the newly formed State of Texas invalidated Mercer's Colony (among other colonies), but the state's supreme court overruled this and allowed the successful grantees to remain. However, the "Texas Association" never was compensated for its colonization plans. Oops.
Mercer's Colony wasn't in existence for very long, but it's still available to see on maps if you look really hard, like I did the other day.