Note: The coordinates of the NE corner of the plaza in Santa Fe, as scaled by me from a 7 1/2 min. quad are: Latitude 35° 41′ 15" Longitude 105° 56′ 14"
The founding of Santa Fe early in the 17th century coincided with a rapid growth of the science of cartography and the resulting map trade. The technique of engraving a copper plate replaced the older relief block type woodcut maps, making maps cheaper to produce, while the exuberant exploration of the world supplied ever new and more accurate information, along with an urgent demand for better maps.
Spain, isolating its colonial possessions from foreign visitors, contributed least to the pool of knowledge. Unless captured by pirates that infested the Spanish Main, maps made by its explorers tended to vanish into the jealously guarded archives of Seville and Mexico City. This lack of cooperation is responsible for the sketchy information on maps depicting New Mexico. On most European maps the true location of the town of Santa Fe could only be established from reports by the few people who had traveled there. One may assume that the Spanish had a better knowledge of geography in the areas under their control than these maps would indicate.
The oldest existing map of New Mexico, the Martinez map of 1602, shows San Ildefonso, Santa Fe did not yet exist, at about latitude 36 1/4 degrees, or about 25 miles too far north. Most of the New Mexico Indian pueblos are shown slightly to the west of the meridian that passes through Santa Barbara, more than 600 miles to the south in Chihuahua, which in fact they are.
In 1656 Nicolas Sanson d’Abbeville produced a Map of New Mexico and Florida that was a composite of the best information available. He was Royal Geographer to King Louis XIII, who in 1634 decreed that the island of Ferro (Hierro) in the Canaries was henceforth be used as the prime meridian on all French maps. Because it was arbitrarily set 20 degrees west of the Paris meridian, the Ferro meridian (17° 37’45" west of Greenwich) does not coincide with the island that gave it its name. Sanson placed Santa Fe on the west side of the Rio Grande in latitude 36 3/4 degrees, and 260 degrees east of Ferro, a whopping 12 degrees too far west. His "Rio del Norte" originates at a lake near Taos and flows into the Gulf of California.
By 1703, on a map started by Sanson but completed by Guillaume Delisle, the Rio Grande was flowing into the Gulf of Mexico and Santa Fe had moved onto the 270th meridian, where it remained more or less for most of the 18th century.
In the years 1766 and 1768 the Marques de Rubi, a field marshal in the Spanish army, made an inspection of the presidios on the northern frontier of New Spain. With him was Captain Nicolas de Lafora, a trained engineer who kept the official record, who was assisted by a surveyor, Lt. Joseph de Urrutia.
Urrutia drew a map of Santa Fe for which he determined the geographic position of the plaza by making his own astronomical observations. His latitude is 36 degrees and 10 minutes, not too bad considering the quality of his instrument, most likely a cross-staff, of which more than 20 years later another Spanish inspector, Fray Agustin de Morfi, remarked that: "The instruments with which the latitude was taken do not inspire confidence in the observations."
For the longitude Urrutia’s map shows: "262 degrees and 40 minutes counted from Tenerife". It was customary at that time in Spain to reckon the longitude from the summit of a 12,000-foot high mountain on the island of Tenerife in the Azores, from which the meridians, like those at Ferro, are numbered eastward around the globe. Since Tenerife is about 16 degrees and 40 minutes west of Greenwich, Urrutia’s Santa Fe is eight degrees too far west.
But only about ten years later, in the fall of 1776, Fray Francisco Atanasio Dominguez was able to state in his description of New Mexico: "Santa Fe…is about 700 leagues to the north of the city of Mexico… The latitude is 36° 11′ north and the longitude 271." Dominguez was accompanied by the soldier-cartographer Bernardo Miera y Pacheco, making the source of his information no great secret. In fact, the Pacheco map shows the buildings of Santa Fe scattered around latitude 36° 11′ and nearly on the 105th meridian (converted to Greenwich), or within 50 miles of their true location.
The only 18th century Spanish map of New Spain that actually made it into print and distribution was drawn in 1768 by a Mexican cleric in Paris. Jose Antonio Alzate y Ramirez was a prominent scientist and had access to the Spanish archives. He showed Santa Fe at 36° 20′ and at about 108 degrees west.
The best-educated and equipped traveler of the period was the German scientist Alexander von Humboldt. By special permission of the king of Spain Humboldt embarked in 1799 on a five-year exploration of the Spanish possessions in America. Although he never made it into New Mexico he spent the better part of 1803 exploring and mapping in central Mexico. For his astronomical observations he used a 2-inch sextant. He had unlimited access to the official records and drew a Map of New Spain, a draft copy of which in 1804 he gave to Thomas Jefferson, whom he much admired. This map, published in 1809, showed Santa Fe in latitude 36° 15′ and longitude 104° 50′, probably the most reliable information available to the Spanish viceroys.
And that was as official as it got until the 30th day of August 1846, when Lt. William H. Emory of Kearny’s Army of the West established the position of Santa Fe near the northeast corner of the plaza. The latitude, which he determined from 111 altitude observations of three different stars, including 36 on Polaris, was 35° 44′ 06", within 2 minutes and 51 seconds (3 1/4 miles) of the modern value. Emory’s longitude, observed by means of a chronometer adjusted at the meridian of Ft. Leavenworth, was 106° 01′ 22", less than 5 minutes (4 3/4 miles) from the true value. Modern surveying had arrived.